Remember Virgin Mobile? Sure you do -- not long ago the last-man-standing MVNO snapped up Helio, and seemed ready to take its place as one of the few boutique prepaid operations still... er, operating. Well that appears to be all but done and done, as Sprint has just announced a "definitive agreement" to purchase the company for $483 million worth of sweet, succulent stock (which looks to be right about what it was valued at to begin with). It looks like Sprint will pair the acquisition with its Boost Mobile brand, which till now was in direct competition with VM. It's not quite rival city, however, Virgin Mobile USA was launched as a joint venture with Sprint, and the MVNO glides on Dan Hesse's network as it is. Still, it does seem to be another indicator that the days of the MVNO are certainly on the wane, though Sprint now looks to own the space -- what little there is.