One of the more interesting sites I came across was this Gothic and Lolita verification site. Even more interesting, they actually list examples side by side and have comments on how to tell the real/fake apart. The top part of the menu bar deals with stolen artwork, while the second part deals with stolen design. While a large portion of the site deals with Bodyline ripoffs, they aren't limited to it - example here.
I think it's possible to say that the reason why companies like Angelic Pretty are aware but not outrightly suing companies is because of sites like this. To some extent peer pressure from the customers creates a kind of self-regulation within the industry. If you copy, the customers are quick to point out make their distaste known. Also there seems to be a general....I don't know what to call it.....dislike? ostracisation? against those who wear copied designs. Some of the boards can be rather inflammatory, one of them even saying: 'If they are wearing copied lolita, then they are fake lolitas too' (wow that translated well >___>;;;) Therefore, it makes sense not to sue because the brand companies know their markets aren't going to be rushing for replicas even if they were offered to anyway.
I don't think it's a matter of flashing their brand/money though, the majority seem to think it's a matter of loyalty....to the extent that a girl who confesses to be a BABY fan and now buys Angelic Pretty says she 'feels guilty for not visiting her favourite store anymore'. I didn't ask any questions myself, but someone living in Japan can probably verify that statement.
Anyway I hope it gave you a bit of perspective from the other side about the issue. It's really interesting to say the least.