ThePoodonkis said:
http://www.youtube.com/watch?v=5GbjXvH7xJA
http://www.youtube.com/watch?v=vvQUhzMHk98&feature=related
The first on is effective, this second one just seems to have an echo effect with the environment.
I don't think a 22 would get through a Kevlar vest, let alone kill someone, to be honest.
And the second is loud, you can only hear it a bit in the video, but I bet you that guy's wearing ear protection.
Now I'm no expert, but it just seems like for the most part, without using seriously specialised gear for ranges where you might just be better off stabbing people, silencers are pretty pointless unless you're hunting game or trying not to annoy the neighbors with your hobby.