One of my favorite personal blog posts is about not trapping users’ data. In late 2006, Eric Schmidt declared “We would never trap user data.” Many of the major Google properties (search, Gmail, Calendar) make it trivial to export or download your data.
In the past, Google Docs would let you export a single doc at a time, but Google Operating System runs down exactly how to batch export your Google Docs. For each type of document (text document, presentation, spreadsheet, etc.) you can choose what file format to get.
I had about 81 personal docs (~13MB) and it only took about a minute to bundle the files up into a .zip file that my browser automatically downloaded. If you have a ton of files, you can choose to get an email when the .zip file is ready.
I really like this feature. By making it easy to leave Google, I think people are actually less likely to leave Google. Or as Jason Calacanis noted lots of people are happy just to get a backup.
By the way, read more about how Google lets you export your data at http://www.dataliberation.org/ if you’re interested.