Well you question is pretty broad. Prosecuted by whom? What obsenity law?
2257 is not about obsenity... it pertains to record-keeping as proof of age for employees.

Are you concerned about prosecution from local authorities? Or are you concerned about presecution from the US Department of Justice?

Your local district attorney might wake up tomorrow, see that he needs to run for re-election, and decide to conduct a sting... if there is some kind of law they assert you are breaking. For example, cities have closed bathouses by enforcing zoning ordinances.

As far as the Dept of Justice... Lee is correct - no prosecutions.

One thing I have certainly realized in this business.. the current landscape of federal criminal laws makes the DOJ horribly inefficient in its job. It is probably is a good statement on how ineffective federal criminal laws are in general. (and why a federal hate crimes law is a bad idea...because no one would ever get prosecuted)

Just some thoughts...
Steve