I think that most want-to-be racers on the MUPS have no real ridding skill what so ever. I commute on a MUP, I see alot of groups of riders 5-9, all on their aero bars, going about 20-25 mph.
I have met some and asked them to not all ride that way, because of the danger of crashing as well as the others that use the paths. They told me to go to H**l. I had no idea what I was talking about. (silly want-to-be s).
I also have trouble with singles that ride up behind you and don't tell me they want to pass. A simple "on your left" would do.
Or people who unleash their dogs on it, who in turn want to chase after the bikers.
Oh well, such is the life on the city run MUP!