Are there any examples of crimes that many people have probably committed? Maybe software piracy, but isn't that just a fine? And I hope that isn't the only example.
Have you ever ordered anything off Amazon? Did you declare and pay the appropriate use taxes for what you bought? Did you ever discuss with anyone that buying things off Amazon meant there was no tax?
Depending on where you live, that's tax fraud and conspiracy to commit. If you had the discussion over email or on a message board, then it's an inter-state crime...
http://www.dumblaws.com/random-laws
They've basically "al caponed" the entire US. If they can't get you on one thing, they'll get you on another. Oddly enough, taxes are probably something everyone has broken the law on. Do you really report everything to the last penny? No? Oh, well theres tax evasion.