The problem with some of the videos is that they highlight abuses and so people might give up veg*nism when they find out about ways of "producing" meat or whatever without those abuses.
On the other hand, I think they are a good wake-up call to how humans treat other species - something which is largely hidden and ignored in society. After you "wake up", you may believe not only that the abuses you see are wrong but that all exploitation is wrong.
In short, I think they're effective and a good idea.
"and I stand
upon a mountain
made of weak and useless men"