The sheriff is not likely to be the one, the FBI or homeland security or ATF or SEC or other feds are the ones who might notice. These are very serious people.
Child porn or picking up minors or terrorism can get you in prison. Fraud, conspiracy or espionage could do it, too. So can hacking.
Your basic porn will not, it is not illegal in the U.S. On-line gambling is illegal, but you are very, very unlikely to be prosecuted. Slander or stealing music/movies can get you sued (even bankrupted), but criminal prosecution is quite unlikely.
Now, I am not an attorney, and I certainly am not your attorney. Talk to one if you have real concerns about any this stuff.