Is Google Docs Bad?

Although Google Docs is a useful tool, many people have serious concerns about it. Just how private are the documents? For one thing, Google collects information for Ad Sense (those Google ads that are targeted at an individual). What other information might be gathered? What if Google became less friendly and started selling information to companies? What if U.S. Homeland Security decided that they should have full access to all the information Google collects? Don't get me wrong, I *do* use Google Docs and find it quite useful but it's better to be aware of the possible drawbacks.