This is trivially done. Check the total of BTC in the DB and compare it to the exchanges BTC wallet(s). Perhaps before each withdrawal.
It's most likely the exchanges have many such checks already in their code.
Exactly, it's simple to compare how many BTC are actually there to how many should be.
If any of the other exchanges aren't doing that I'll be surprised and disappointed.
-Jered
The point is allow customers to verify their account BTC balances independently of the exchange. This can be done by assigning each
customer a single wallet address. The customer can check their balance using block explorer. If money in the wallet doesn't match the customers accounting, then
a) their account has been hacked, or
b) the exchange is using a fractional reserve
This is my point exactly, you also get the TRANSACTIONS when you buy bitcoins they will list everyones wallet that you bought from.
Saying just to look at their wallet is stupid. Obviously when you take BTC some will come out, but you don't really know what the database says they have.