I honestly beleive that we are just at the tip of an MF Global type (gold derivatives exchange that failed last year stealing millions in 'segregated' client assets) epidemic among Bitcoin exchanges that got caught with their pants down during the BTC crash last Thursday.
You see a Bitcoin is simply a derivative that only represents the LOOT that the guy that you got it off, got out of you for it, and made off with. It is a fiat "futures derivative contract" that arguably has some but really has no certain value/worth.
Like a "gold contract' or "mortgage backed security' (love that last word) derivative it is a "BTC Futures Contract" that merely allows you to keep, transfer it in, transfer it around or transfer it somewhere else to resell it there for whatever it may seem to be worth to the next guy, a minimum of an hour from now.
Now if the exchange you have an account with was dealing honestly on the up and up it should religiously keep all client funds in segregated client accounts THAT IT DOES NOT TOUCH nor ever figure into it's own net earned assets nor gross daily "take". It should immediately convert all transactions in real time and transfer all cash funds from buyers accounts to sellers accounts, removing it's fees only. It will have ZERO problems conducting business as usual any more than it ever did taking in, trading and paying out your money on the way up. Your account is your property, not theirs.
But if the "Exchange" has been "reserve bankstering" they may think it advantageous to delay redemption trades or simply "reserve" cash floats (minimize their bank balances, reported gross) by keeping client asked-converted-cash tied up along with client bid-spent funds in the "lay around" medium that profits them most,
meaning they keep most all of their day to day "floats" in (rising) appreciating/deflating Bitcoin Futures instead of letting much lie around in real (stable) cash. This way they get to play the game with "money" that's not theirs (steal) and pocket the gains, not waiting for client bid trades, while clients wait for them to debit deposits to accounts or to pay them cash withdrawals out of fresh cash or BTC arriving daily from new depositors.
To simplify, imagine they just take (and keep on taking) all the (spare) loot they get their hands on and buy
themselves one huge commingled "reserve" pool of BTC with it. Then, always later, clients must just buy and sell from them within their own "reserve" pool. You loan them your loot for free, later, they then lend you an account for fees. They get to trade and make/take the profits off their commingled "reserve" of Bitcoins ASAP all the time. You get to Convert "your" (still theirs) Bitcoins in and out of their pool for fees, and you (on your comfy recliner on their pool deck) also get to lend them your converted loot for free until they are good and ready to pay you back so you can go home to shower.
Thus, after a huge crash a negligently managed Exchange just lost itself and all it's clients a boatload of value, needs to hire a new "emergency trading team" and suddenly can't even pay withdrawals, claiming that "they are urgently hiring and training more people due to volume" or that they were "overloaded" or that they have "too many emails" and "annoyingly dumb customers" to "get back" to.
If you withdrew funds on Wednesday night and your exchange used to normally take their good old 2 days time to put money back into your bank and they don't answer the phone or any emails and you now suddenly see 4 days gone by and your withdrawal order hasn't even been sent by them yet (today at 4) and they posted a last Friday lunch break News statement like:
April 12, 2013, 12:39 p.m. - *** IF YOU ARE WAITING FOR A RESPONSE FROM CUSTOMER SERVICE - CLICK HERE ***
We are responding to every e-mail and voice-mail and
currently have a list of 400 customers to get back to due to the high volatility. We have also just hired 6 more staff dedicated to customer service and account verifications. The most common inquires we get are from people failing to read the Deposits and Withdraw Funds link above fully. We also have a youtube video Depositing with XxxxXx, please watch this video as well as the trading video on our channel by clicking on the youtube icon above. If you have made a cash deposit you MUST have a corresponding open deposit request shown on Deposit Funds when logged into your account, this involves pressing DEPOSIT and then CONFIRM on the next page.
We do not process RUSH cash deposits, we have a dedicated team processing cash throughout the day. EMT's have been disabled due to the xxx closure, we are taking steps to re-enable them with different banks and payment providers with much higher limits in the coming weeks, in the meantime unverified users can withdraw via direct deposit and by filling in their banking information.
There is an up to 5 business day delay on receiving a direct deposit to your bank account. If you sent BTC to your XxxxXx account and you have 6 confirmations with no balance increase 
please logout and then back in. Please be assured that
we are working as hard as we can to hire resources, get back to every customer inquiry and decrease processing times for all payments.
In spite of the fact that their Terms of service indicate:
Direct Deposit to your Bank Account
If you have a Canadian bank account you can enter it via the Banking Information page when you are logged in. You can then initiate a request for withdrawal that will be directly deposited into your Canadian bank account. If the next day is a business day, the cut off time for direct deposits is 10PM MST. All deposits received before this cutoff will be deposited in your account within 1-2 business days. Note that weekends and bank holidays are not considered business days and each bank has different delays. In rare cases, it may take longer than 2 days.
...and you've also clearly noticed in the past that they never ever seemed to have had any problems with withdrawals before
when all the same "volatility" was going up I'll give you three guesses what is going on with your withdrawn money, and those Bitcoins that are now mysteriously "getting lost" on their way into their accounts....
