It is definitely illegal.
My 10 cents on the matter…
The BETonSPORTS case is a ‘test case’ and we are unlikely to see other prosecutions for a while of this magnitude. But if we do, it will be against those operations that take telephone wagers. Customer support is one thing, and accepting bets over the phone another.
If you believe that the US prosecutors will ‘win’ in the BETonSPORTS case, then you should start looking at Internet-only shops.
Bear in mind though that I myself do not expect trouble for those other operations who are now taking telephone wagers for the forseeable future. However, if in the future you expect BETonSPORTS to set a precedent, and there to be a wave of future prosecutions, you should consider only those sportsbooks who have never taken telephone wagers.
Because, you know that the Federal prosecutors will have already obtained evidence against the high profile sportsbooks of today in that regard before they leapt on David Carruthers at the airport.
(An excellent guide to the ‘Wire Act’ is the book ‘Cutting The Wire’ by David G. Schwartz. Click on the book cover from the FreeDavid site to see an overview of the book, and consider ordering it via Schwartz’s site.)