I'm a member of a US based fixed forum and I know the admins on the site are extremely concerned to the fact that you alluded to - most of the revenue from the site actually comes in the form of sponsorship from other sportsbooks, even moreso than client money
Interesting times ahead....
BG - Most likely will be closed unless they are bought out by someone. I work over at UltimateCapper and the owner has already been talking to a Canadian company about them buying them out. Otherwise they'll either have to have services sponsor them or sell picks on the main page. Most of these ideas won't generate enough money. At this point sports gambling forums have all but one choice and that's to sell there site to a company based outside the US. Otherwise the site is illegal once Bush signs the deal.