None of the wing chun clips posted are representative of real wing chun... the first two practitioners are terrible and the cheung vs boztepe match is a grudge match between two bitter enemies, and cheung's style is most definitely not considered street effective by other lineages...
the problem with the first two clips is that they are immobile and just stand there and let themselves be taken down. striking
works - look at the sakabura vs. royce gracie fight, sakabura kicked his ass because he had striking skills and didn't allow gracie to take him to the ground... now sakabura is a kick boxer as well as grappler, but the principle is the same - a good wing chun striker won't be taken to the ground easily, and will then strike to the eyes or whatever it takes to get back up.
gary lam is a good wing chun guy - check out this, which is more representative of what wing chun should look like:
http://www.garylamwingchun.com/GaryLam.wmv and the vids on this page:
http://www.garylamwingchun.com/movies.html - it should be noted that he is also a champion kick boxer and kick boxing trainer, and was trained by the same guy that did most of bruce lee's training (wong shun leung).
the bottom line is that in a
real street fight, which is what this thread is about, rather than an artificial ring situation (no eye/ groin/ throat strikes), against
multiple opponents, you simply cannot go to the ground... b/c as soon as you do the guy's buddies will just kick the shit out of you, you are fucked. you
have to stay on your feet and strike your way out and escape.