well, I'm no hardcore bmx feind, but I had an old arse bike where the pegs had threading and they were used them instead of nuts. Then I got my newer haro and those pegs didn't have threads, they were more like washers with an extra part you could stand on. The bad part was you needed a deep socket or an extention to your ratchet to get them on and off.

As for the debate on whether they'll destroy a track hub, I imagine the high end, expensive track hubs would get destroyed by a set of pegs because those are made for racing, not for sturdiness. (saving weight everywhere possible) I'd assume a cheaper, more hefty hub would fare better... and would cost less to repair/replace.