"Stravervals" is what I call them. Some days I do my intervals from one underpass to another, and of course that is how people broke up the segments on this particular MUP. The end result is I end up being in the top few people out of 1000 on a segment sometimes. All my rides are solo though, and on a short enough segment (<1.5mi?) I doubt a group really has much of an advantage.
My intervals were done like this long before I heard about strava, and I have to assume others are out there doing something similar so I don't feel too bad about it.
Anyway, if you're using a group specifically to take down a strava KOM I guess its fair game, but it does seem kinda lame.