There is no reason for coinbase to Hold your account transaction for 4 days other than trying to get your personal information which is bs in my opinion.
how about making sure your funds clear? coinbase works differently compared to other exchanges. when you place an order, CB reserves those bitcoins and waits for your payment to clear.
Other exchanges, like MtGox, force you to send your money first - which takes around 4 days depending on deposit method. Dwolla, for example, takes about 5 days. And then another 30min to an hour from Dwolla to CampBX.
As you can see, the hold is still present, the only difference is whether its before or after you place your order.
source: I've done business with CampBX and Coinbase.
I understand Banks take a long time to transfer the money back and forth but look at something like paypal for example, its instant. its purposely done to force its user base to give up personal information for ease of use.