One reason I particularly avoid logging in with Facebook or Twitter is the large proportion of sites that will abuse the authority to post whatever you post on

One reason I particularly avoid logging in with Facebook or Twitter is the large proportion of sites that will abuse the authority to post whatever you post on your FB/Twitter profile as well. Sorry, if I'm just signing in to comment on a Twitter-shared picture or a news article, that does NOT mean I want it posted on my message stream! I've learned the hard way to always use Google/Yahoo OpenID auth instead.