Twitter, actual categories for accounts, or at least individual tweets. Science, tech, entertainment, news, my blog sort of thing. Trying to get anything meaningful from that tag system is a horrendous task. The only people not using that particular tag at the time are generally those in the know that you're trying to find.
FB? A hard limit of 3 status updates per person per week. A real point to the site. Take the secondary school off of education options, it really doesn't mean shit and is useless information. More options than "Like", a lot of the time it's not appropriate, Disliking someones post can be a positive thing depending on context.