I believe you actually need a license to use it, even at home, non-commercially, under U.S. doctrine of what constitutes "practicing" a patent (but this is rarely litigated, for obvious practical reasons).
They might not get arrested but if someone on hacker news stated the completely false claim that it was legal, just like you did (twice!) for H.264 further up this thread then they'd probably expect to be corrected by someone.
(I'd also assume that some poor, probably non-white person has gone to jail for exactly this kind of law that everyone ignores.)
Well, remember that most people in the world aren't from the US. It's like saying "you can't say whatever you want on the Internet" because in China you can't.
You also can't in the US, UK, Germany, France, Spain, Italy, etc. There might be some country where speech on the internet is completely unrestricted, but its population is likely too small to matter except to bittorrent operators.
Yeah, in practice you'd have to be using it in a way that someone would notice. I believe there's some 19th-century precedent on it being illegal for farmers to make DIY versions of patented tools, even if they never bought or sold them--- just making and using them was a patent violation. Presumably they were somehow obvious enough for somebody to notice.
