It's well past being solely an aggregator.
LinkedIn is a good tool for viewing someone's public resume, though I don't regularly log into it. Every once in a while, I'll log in to check out how a previous employer is doing (e.g. see which of my ex-coworkers are still at the company, what new positions have been created, etc.). I still have dozens of unanswered connection requests from recruiters, though (I don't accept people I don't know), and the site has gotten progressively spammier over the years.
Joking aside I almost never get followed by spam accounts on g+, weekly or more on my English speaking twitter account.
- LinkedIn: The worst of the worst ... :D
- HN / Reddit / Twitter: How do you share pictures privately with friends? (to name one necessary feature)
Further, HN/Reddit/Twitter etc. each only have a subset of my friends. ALL of my friends are on FB.
Flickr. Some of the holes in the group management are a weakness there (no albums in Groups, for example).