I feel like people maybe flipped out a little more than necessary, so I want to remind everyone that Yahoo tends to beat websites to death and then leave their corpses in the street – Del.icio.us was an anomaly in that respect – so it’s not like Tumblr’s going to disappear tomorrow. If Yahoo sells Tumblr we’ll hear about it first and have time to take appropriate measures.
(Who the fuck would buy Tumblr? Microsoft. Microsoft, owner of Bing, would buy Tumblr.)
That said, BACKING STUFF UP IS A GOOD IDEA. BACK UP YOUR SHIT. DO IT, LISTEN TO YOUR INTERNET FATHER. You know when I learned this? When in 2008 my livejournal was hacked and I lost five years of my life. I resurrected about 80%, and you know where that 80% came from? Google cache, Archive.org, and notification emails people happened to have saved. BACKUPS. And even then I had to copy and paste every post and repost it backdated. It took me eight months.
When del.icio.us was sold, data was lost, but more importantly, the data that remained had to be moved, which was when I discovered that about a quarter of the fanfics I’d bookmarked were now deleted, locked, or otherwise missing (this was pre-AO3 but fanfics can be deleted from AO3, and they can be deleted from Tumblr). I rescued a few from archive.org but I also lost a good number, which is why I use Evernote to archive not just the URLs but the stories themselves.
No technology is infallible, unhackable, virus-proof, or incorruptible. Back up your hard drive, or at least the parts with your favorite music and family photos. Back up your tumblr, or at least the entries that are important to you. Love that fanfic? Save a copy of it.
You know what happens to people who don’t back up their shit? They get sanctimonious but ultimately correct lectures from Reed Richards.