from my experiences with bank of america with 4 disputes including one amounting to $890 in identity theft charges (money spent on a adult entertainment site) they took care of it immediately. i had to fill out a piece of paper saying i didnt make those purchases and they refunded the money immediately. 3 disputes were for cheap stuff ($50 calling card, $75 ebay purchase, $300 ipod from apple) comparatively. no problems happened there. with the $890 issue, a credit collection agency came after me and i got the police involved eventually and a call from the police officer helping me got the credit collection agency off my back immediately.
wachovia held me responsible for a $22 charge i did not make. refused to cover it even though i didnt make.
should be obvious which institution i bank with now.