Defending against one of these suits is simple. Simply ask that the case be dropped becuase Ascap (or whoever) has shown no evidence - at all.
If they have evidence, then you should be paying the fees.
BUT if the establishment plays a single CD in the business (regardless of licensing), they would still be a target for the shakedown.
AND just to let you know where Obomber stands:
Obama picks RIAA's favorite lawyer for a top Justice post (CNet January 6, 2009 Declan McCullagh)
Will Obama's copyright czar help save the music? (Yahoo news Sat Nov 15, 2008 Antony Bruno)