Check out the "introductions" thread – you'll find information about everyone there.
Although, I don't like that everyone calls themselves a parkour enthusiast these days, just because they can do a few tricks.
As for Yamakasi, they're great because of their tricks. It immediately makes you want to achieve the same.
Added 12 minutes later
No, but in general, parkour training itself doesn't stand out as something special. It's just strength and flexibility training. There are also some "mind exercises" – simple relaxation techniques, and even simple meditation is more effective.
In short, if you're strong and agile, even if you just do squats and push-ups at home without taking any "courses," you'll be able to run and jump over fences just as well.