I would argue that a fighting technique is the same way. It's entirely possible for someone to have a punch or a kick that is "bad form" but still effective, though once it's been proven to be effective it's no longer called bad form . . . it's called unorthodox.
Absolutely. There are some bad-*** street fighters out there. No doubt. However, I don't know of many street fighters who didn't learn by losing a lot in real street fights. Their school involved getting beat up until they figured out what people are likely to do in a fight and stopping that and getting their own licks in.
However, I've also seen a lot of videos of street fights with two lunkheads duking it out, maybe both throwing relatively powerful blows, but just some serious sad sack technique. A trained martial artist would just tear them apart by exploiting all the holes in their unorthodox self-made style that they didn't know they had, because their equally sad sack opponents didn't realize they were holes that could be exploited.
Good example? Kimo.