I used to do that, but it would sometimes break functionality on certain sites, and the whitelist is a bit of a pain to manage. I've had good success with http://disconnect.me
1) Disqus-like commenting systems (I don't use them)
2) Diigo bookmarklet (whitelisted)
3) Youtube liking/favoriting at the time when they tried to marry it with Google+ (fixed now)
And I think that's it, can't recall anything else.