I would like to point that at that time, there probably wasn't any properly functioning and user friendly decentralized exchange (that I was aware of). Now they're starting to appear.

Decentralized exchanges can prevent most of these issues, mainly database errors, malfunctions and hacks.

I'll follow up with a timeline of issues that have cost users millions of dollars.

04/01/2015 - Bitstamp Hacked - 19000 BTC Stolen

https://www.bitstamp.net/article/bitstamp-is-open-for-business-better-than-ever/

15/02/2015 - Bter Hacked - 7170 BTC Stolen

http://www.coindesk.com/bter-bitcoin-stolen-cold-wallet-hack/

02/2015 - Bitfinex - Claims of Potential Frontrunning

https://www.reddit.com/r/BitcoinMarkets/comments/2t3iz5/bitfinex_cso_phillip_g_potter_admits_to_trading/

16/03/2015 - Allcrypt Hacked - 40 BTC stolen

http://themerkle.com/news/allcrypt-bitcoin-exchange-hacked-over-40-btc-in-funds-stolen/

25/03/2015 - Cryptoine Hacked - Hot Wallet Compromised and Emptied - Undisclosed Amount

http://www.zdnet.com/article/bitcoin-exchange-cryptoine-hacked/

05/05/2015 - Ukrainian BTC-TRADE Hacked - 30 BTC stolen

http://forklog.net/ukrainian-bitcoin-exchange-btc-trade-hacked-again/

22/05/2015 - Bitfinex - Hacked - Undisclosed Amount

https://www.cryptocoinsnews.com/breaking-bitcoin-exchange-bitfinex-hot-wallet-hacked/

https://www.reddit.com/r/Bitcoin/comments/36uxxz/bitfinex_has_been_hacked/

01/06/2015 - Blockchain.info - Sends 34 BTC to the Wrong Address

http://www.newsbtc.com/2015/06/01/blockchain-sent-8k-worth-bitcoin-to-wrong-address/

10/07/2015 - OKCoin - DDOS Attack

http://blog.okcoin.com/post/123893357479/regarding-july-10th-ddos-attacks-explanation

21/07/2015 - Igot - DDOS Attacks

https://twitter.com/iGotcom/status/623488879815831552

30/07/2015 - Igot - Scam Accusations - Delayed Withdrawls

http://www.coindesk.com/bitcoin-exchange-igot-challenges-scam-allegations/

18/08/2015 - Bitfinex - Flash Crash and Issues with Margin Trading.

https://soundcloud.com/whaleclub-bitcoin/bitfinex-ceo-recording-after-18082015-flash-crash

https://twitter.com/btcWhaleclub/status/633820388938653697

19/08/2015- CEX.IO - Theft Accusations - Missing Funds from User Accounts due to "Fees"

https://bitcointalk.org/index.php?topic=318010.msg12185497#msg12185497

16/08/2015 - Bitcoinica - New Leads about the 40000 BTC Stolen

https://www.reddit.com/r/Bitcoin/comments/3hzfeb/bitcoinica_theft_of_40k/

https://www.blockseer.com/g/63dtw2vOqka6 https://www.youtube.com/watch?v=AypRF9q0llU

4/08/2015 - Bitfinex - Halts Trading - Claims Issue with Post-trade Processing - 15000 Gox BTC Moved, 5000 to Bitfinex - Coincidence?

https://www.reddit.com/r/BitcoinMarkets/comments/3i5thz/daily_discussion_monday_august_24_2015/cudrtfc

https://www.reddit.com/r/Bitcoin/comments/3i6p5s/15000_coins_from_may_2013_bought_from_gox_moved/

http://btc.blockr.io/tx/info/41d84dccf2487efcca5e35a5ec4a20525d736c4590261fe20a71f8c91962a89e
https://www.blockseer.com/g/n8tcg4pOp92t

24/08/2015 - Igot - Exchange Ceases Trading - Ceased All Public Communications Over 1 Week Ago

http://siliconangle.com/blog/2015/08/24/australian-bitcoin-exchange-igot-ceases-trading-may-have-been-an-indian-based-scam/

25/08/2015 - Bitfinex - Trading Halted - Claims Data Corruption Issues

https://twitter.com/bitfinex/status/636258874606133248

27/08/2015 - Coinbase - Claims of Exchange being Down

https://www.reddit.com/r/Bitcoin/comments/3ijnqd/coinbase_down/
http://i.imgur.com/038663J.png

31/08/2015 - OKCoin - American USD, Litecoin, and Bitcoin Deposits Banned - Regulatory Issues

http://bitcoinist.net/chinese-bitcoin-exchange-okcoin-stops-accepting-american-bitcoin-deposits/

03/09/2015 - Coinbase - Customers Charged Twice - No Refunds

http://altcoinpress.com/2015/09/breaking-coinbase-decides-not-to-refund-customers-in-double-billing-glitch/

http://www.econotimes.com/Coinbase-to-credit-user-accounts-with-bitcoin-in-double-billing-glitch-84870

04/09/2015- Blockchain.info Down - System Maintenance

https://twitter.com/blockchain/status/639815205862641665

http://www.coindesk.com/bitcoin-wallet-provider-blockchain-currently-offline/

17/09/2015 - BitPay - 5000 BTC Stolen

http://qntra.net/2015/09/bitpay-claims-hack-amounting-to-5000-bitcoins/
http://cointelegraph.com/news/115289/bitpay-hacked-for-over-18-million-in-bitcoins

https://twitter.com/BlockSeer/status/644346233612431361

https://www.reddit.com/r/Bitcoin/comments/3l9l6ythe_bitpay_chain_of_events_documented_by_hanover/

17/09/2015 - BitReserve (now Uphold) - Claims of Blocking Withdrawals

https://www.reddit.com/r/Bitcoin/comments/3lbqlk/bitreserve_account_blocked_with_46k_eur/

https://www.reddit.com/r/Bitcoin/comments/3kos8k/public_ticket_to_bitreserveorg_can_not_withdraw/?

20/09/2015 - Cryptsy - "Steals" 0.5% of Every Deposit - Fees Increased - No Prior Notice
https://www.cryptsy.com/pages/fees

https://www.reddit.com/r/Bitcoin/comments/3lnipw/cryptsy_increases_withdrawal_fees_to_05_with_zero/

19/10/2015 - Cryptsy - Claims of Exchange Refusing to Pay Out Users

http://siliconangle.com/blog/2015/10/19/bitcoin-exchange-cryptsy-may-have-gone-full-mt-gox-refuses-to-pay-out-customers/

https://www.reddit.com/r/Bitcoin/comments/3pbk88/bitcoin_exchange_cryptsy_may_have_gone_full_mt/

5/11/2015 - OKCoin - Cyber Attack

http://cointelegraph.com/news/115562/biggest-bitcoin-exchange-okcoin-suffers-cyber-attack-price-plummets

10/11/2015 - OKCoin - Malfunction Causes Liquidation - LTC bought at 1.5CNY, sold at 19CNY

https://www.reddit.com/r/Bitcoin/comments/3sb0dx/regarding_okcoin_ltccny_price_error_resuming/

https://www.reddit.com/r/litecoin/comments/3s96j6/look_okcoin_millions_of_litecoins_dumped/

14/11/2015 - Gemini - Looses Credibility - Trades Reversed

https://www.reddit.com/r/Bitcoin/comments/3ss945/just_got_this_email_from_gemini_about_the_2200/

https://www.reddit.com/r/Bitcoin/comments/3sqjrf/gemini_2200_per_bitcoin_are_they_out_of_bitcoin/

24/11/2015 - Kraken - DDOS Attack

https://twitter.com/krakenfx/status/669302757552074752

http://www.bitcoinfuturesguide.com/bitcoin-blog/kraken-has-received-extortion-letter-suffering-ongoing-ddos-attack-will-not-pay

https://www.reddit.com/r/BitcoinMarkets/comments/3u5few/kraken_experiencing_ongoing_ddos_says_they/

30/11/2015 - Arthur Hayes on Chinese Exchanges - Operating as Shadow Banks

https://www.reddit.com/r/BitcoinMarkets/comments/3uv7lt/arthur_hayes_of_bitmex_only_logical_explanation/

http://www.bitcoinfuturesguide.com/bitcoin-blog/arthur-hayes-of-bitmex-chinese-exchanges-are-operating-as-shadow-banks

03/12/2015 - Gemini - Trade Reversal Could Be Unjustified

http://cointelegraph.com/news/115785/bitcoin-trade-reversal-on-geminicom-could-be-unjustified

05/01/2016 - Cryptsy - Lag Claims - Trade Engine and Withdrawals Paused

https://www.reddit.com/r/Bitcoin/comments/3zm3m7/cryptsy_halts_both_trade_engine_and_withdrawals/ http://www.coindesk.com/altcoin-exchange-cryptsy-takes-trade-engine-offline/

07/01/2016 - BTC-E - DDoS Attack

http://forklog.net/two-exchanges-experienced-ddos-attacks

https://twitter.com/btcecom/status/685125259872354305

08/01/2016 - Bitstamp - DDoS Attack

http://forklog.net/two-exchanges-experienced-ddos-attacks/

https://twitter.com/Bitstamp/status/685398977924206592

09/01/2016 - Bitfinex - Claims of Underpaying Custumers

https://www.reddit.com/r/BitcoinMarkets/comments/401dne/is_bitfinex_underpaying_margin_funding_again/

09/01/2015 - Cryptsy - Finally Goes Rogue?

http://bitcoinist.net/cryptsy-has-moved-out-of-their-building-unannounced-nowhere-to-be-found/

https://www.reddit.com/r/Bitcoin/comments/4050h3/cryptsy_has_moved_out_of_their_building/

http://bitcoinist.net/timeline-cryptsy-disappearance-mystery

10/01/2015 - Coinbase - Peter Todd Double Spends

https://twitter.com/petertoddbtc/status/686362883756695553

http://bitcoinist.net/peter-todd-double-spends-on-coinbase/

Useful Links with more Events

Consumers' Research Bitcoin Loss Calculations (since 2010)
Coinbase's Incident History

Now we have some options, namely OpenLedger, which is seeing an increase in volume. Remember if you don't own the private keys, you don't own your crypto.