The venues can't come after you, because the act of recording isn't illegal. All it does is break the contract you entered into when you bought your ticket, and since all they can legally do for breaking that contract is kick you out of the venue, you've got nothing to worry about. If it's Guster, post on archive.org - I've got a few recordings of no-recording-allowed shows but the band doesn't care, it was just the venue/promoters/headlining act being a pain in the ass.