Add a comment and you stand a good chance of being verbally abused. I have also seen the most hateful comments when the videos are about disability, disfigurement etc. There is racism, sexism and homophobic comments. Nothing is done ever. Shame really because youtube can be really entertaining and informative.
The site itself is great, but some videos aren't for kids, as well as users will try to scam you. But those are users and they don't represent the site as a whole, so in my opinion, youtube is awesome.