It's funny, I think Yahoo has done this twice now: once with Tumblr and once with Delicious (although the chain of ownership for Delicious is much longer).
Yes, I forgot about Delicious. Yahoo destroyed both of those companies. Unbelievably all the Delicious data is still available. Delicious was one of the only accounts I could log into after eight years in jail. It was amazing to see that 99% of my bookmarks were dead links.
