They already do have something of the sort set up for running - when I've uploaded a ride when my Garmin was set to 'Run,' I've gotten an immediate flag from Strava, but I guess that the tolerances are pretty loose on rides. I'm guessing that it's just looking at speed and, with the speeds attainable downhill and/or in groups, the window of legitimacy needs to be pretty wide. If enough paying members start asking for it, I'm sure they'll work on it, factoring in grades and whatnot, but until then, I'm sure that the focus is on facebookification of the platform.