I've looked at new shiny bikes at a couple of different bike shops, and I always ask about racks (partly because at the time I was unsure if I wanted a new bike to do everything, commutes and grocery runs, or just be for long fun rides). Anyway, I've been told you can definitely put a rack on an entry-level road bike (Trek 1000, for instance). I don't know how quickly that falls off as you move up, though. :)