In the last few months:
- Tumblr purged adult content (and a bunch of stuff it misindentified).
- Flickr purged free storage above a limit of 1000 photos/account.
- Myspace deleted 12 years' worth of music.
And Google+ only has two weeks left before Google pulls its plug.
Back up your accounts!
And if you can, consider donating to the Internet Archive. https://archive.org