I don't mind these at all. Maybe it's a result of LA, NYC, then Austin, where they are definitely part of a "look" - a little bit punk, a little bit saucy, a little bit lazy. But so long as they're clean, and it's obviously intentional, I really don't care - especially for black ones under a black tank top. Or the thin white straps for my bra-in tanks.
Now, I do mildly mind seeing people's entire brassiere or nipples through tops, but mostly because 1) it breaks up the line of a shirt, and 2) I know I will never get any male in the vicinity to listen to a damn word I say until those bratty boobies beat it. But the straps? Meh.
Am I missing a ladylike gene? It does seem that many on the forum are much more sensitive to a flash of fantastic elastic.