let me crunch some numbers (please tell me if i made any errors anywhere):
- deposit $1000 to bitstamp and pay $5 fee
- buy $1000 worth of bitcoin in (on? at?) bitstamp at $1170.88 you pay $2.5 fee and get 0.85192333BTC
- withdraw bitcoin to kraken and pay nothing! or 0.1% with bitgo (apparently)
- sell bitcoin at $1186.54 and get $1010.54 and pay $2.62 fee so you are left with $1008.21
- withdraw to your bank and if you pay the same fee as bitstamp you end up making $3.21
this is 0.32% profit. if you think the risk is ok such as price changing up and down, withdrawals getting stuck and taking long, ... then do it.
It's possible to up the 00.32% figure, but the arbing would have to be done at high volume to make worthwhile money and then there is the problem of USD trading liquidity at these exchanges as alyssa85 and serje mention.
There are also potential problems moving large sums by bankwire out of a US bank and back.
Likely that some accounts would be closed, as US banks are afraid of being accused of aiding money laundering and they are too short sighted (and basically stupid) to accept bitcoin arbing as a legitimate financial activity.