Hipsters are also people who are in or about a scene and either make or talk about making shitty art - though such can involve working in a book shop, record store, used clothing shop, etc. By definition. I'm not sure, though, about needing a strong metropolitan setting. South Dakota may have hipsters, but the very nature of South Dakota, I don't know how hip they could be, because I don't know what sort of scene SD could have that they could be a part of. SD may have a burgeoning punk scene, but I think since there is no contrast, it may be legitimate and not ironic.
More than ironic T-shirts, the culture embraces bad taste and celebrates it. Whether or not that look can transition from bad to good is in the eye of the beholder.
The other thing about hipsters is that they are either upper or middle class people who desperate pretend to be lower class. They may have spent $200-400 dollars on the ensemble, but it shoud look like it cost $25.