- Your Google Search history.
- Your Google Talk chat history.
- Google Wallet and Google Checkout details, including credit card information and a history of purchases.
- YouTube materials, including videos you liked, shared, or uploaded.
- Posts created with Blogger, or comments you've left on Blogger sites.
- Google Calendar entries.
- Google Health data.
- Bookmarks stored or synced with Chrome or the Google Toolbar.
- Google Latitude location information.
- Anything related to your Android phone, including your account or your Android Market downloads.
- Anything involving Orkut, AdWords, Google Finance, and more.
That list surprised me, not just because it's so long, but also because Google does retain data for most (if not all) of those services. Your Google Search history can be accessed here, for example. Why doesn't Takeout let you download this information instead of shipping you off to another site?
If you want to get an offline copy of any of this information, your best bet is to check out the comprehensive list of how-tos at the Data Liberation Front, managed by the group of Google engineers that coded the Google Takeout service. Here you'll find detailed instructions on how to manually get your data out of another two dozen Google-operated services not covered by Takeout.
Liberation vs. Deletion
It's important to remember that with Google Takeout you are getting a copy of the information stored on Google's servers, and are not removing the originals from Google's clutches. There's no way to delete anything at all via Google Takeout.
If you want to delete information from Google, you'll need to visit each service you use and delete the data or the account manually. In Blogger, for example, that means visiting the blog administration tool and using the "Delete blog" link to remove it from the Web. (There's a "nuclear option," too, available at the bottom of your Settings page.)