I guess they're a lot like Brazilian bikinis? Based on what I saw, I imagine they are a little more conservative, but then, I've never been to Brazil.
So, just doing a little thinking out-loud about the wedgie-style or thong bikini here. I totally get the logic of hanging your butt out if you're laying out to tan. I personally hate walking around with a white ass all summer. In this respect, the thong style bikini is an awesome innovation that Americans will always be too prudish to ever adopt.
HOWEVER.
The thong bikini is not treated as a tanning suit here. And it is not worn just by the young and fabulous. For every great butt we saw strutting across the beach, there were two that were just . . . not flattered by their outfit choice. Especially since I saw women doing everything from playing soccer, to bending over to collect sea shells, to rock-climbing in suits much skimpier than the ones below.
I guess, overall, no judgements on my part, it's cool other countries are so much less uptight about body image. I guess I just don't see these catching on at home any time soon.