Especially now that the US has moved to a first-to-file system, there's no guarantee that the patent holder is the inventor. Separately from that, some patent troll companies file obvious, overbroad patents without implementing them (e.g. the classic case being doing <X> on the Internet, of course) to build up their stockpile. Just because they might end up with some patents when their junk sticks doesn't make them an inventor.
