Maciej Ceglowski runs the popular 1 bookmarking service Pinboard.in, of which I'm a happily paid-up user. He recently wrote a blog post on the value of free web services and how free isn't always better:
Were you a big Gowalla fan? Did you like Dodgeball? Did you think Trunk.ly (gasp!) was better than Pinboard? Did you make a lot of contributions to Nextstop? Do you miss Aardvark and EtherPad? Did "I Want Sandy" change your life?
These projects are all very different, but the dynamic is the same. Someone builds a cool, free product, it gets popular, and that popularity attracts a buyer. The new owner shuts the product down and the founders issue a glowing press release about how excited they are about synergies going forward. They are never heard from again.
You might not be that familiar with some of the sites he mentioned, but the idea should ring true for whatever free service you're currently using. It might be free to use, but in most cases it's you that's the product. Google sells advertising based on your use of their free email, search and other services. Same with Facebook and it's free services.
I know, I know. Facebook is too big to ever go away. You're right. Nothing to worry about.
Maciej also wins the award for the best disclaimer on a blog post:
DISCLAIMER: I run a paid bookmarking site. Every morning I wake up and dive into my vault of golden coins.