In theory it's a good idea - like friendly racing, but without the entry fees and precision of expensive timing systems. Lots of people will say that Strava isn't accurate enough, but unless you're doing really short segments, it's really not that bad.
It would have to be broken up into 3 different categories: XC climbs, XC loops and DH/Gravity Enduro descents. There would have to be enough people riding enough nominated segments to make it worthwhile. Obviously these would also have to be broken up into different geographical areas.
It would be really cool to do some Gravity Enduro events where 5 or 6 segments were nominated for a 3 week period where riders could go nuts trying to smash out good times on all of them, the winner being the best combined times overall before the cutoff deadline. Mt Macedon would be a good location and needs to be ridden to death right now as it's being logged soon and will be closed until 2020. There's plenty of good Enduro segments out there to keep people busy and conditions are primo at the moment.