The problem with places like Reston is that if you're a typical two-worker couple there is little chance you're both going to find work in the same suburb. And if that doesn't happen, you're stuck commuting between suburbs, which is usually the worst possible scenario (and a major reason why traffic in the DC metro is worse than in bigger cities). Better to have bedroom cities with stores and shops and shuttle everyone into the core city via regional rail.

Reston would be a great bedroom city if DC had proper regional rail. Standing room only in the Silver line for 45 minutes sucks compared to regional express trains in places like Chicago or NYC.