FAA 400' Limit

If I were, say, to upload a video of my drone at 1k feet (with no visual proof other than how small the trees and such are), and the FAA saw the video, or it got reported, by chance, does anyone know if they really take that rule seriously? I couldn't find anything about them taking legal action against those flying too high. I also saw a post somewhere about how that "rule" might not really be enforceable, I'm not sure though.

Just wondering

Edit: thanks for all the comments-- I understand there is a lot of legal trouble, and by the sounds of it, it seems like right now the FAA does not have a rule restricting you from going over 400', just a guideline. That being said, I'll probably follow that guideline. In the few days I've flown my drown, I've seen man controlled aircrafts flying at roughly 800 ft several times, so I think not only for that reason, but because laws change, and the laws aren't entirely clear. All said, I won't go over 120m (400ft roughly). However, I reckon I will be using the rule that if you are within 400' of a structure you are good.