Actually I don't care, I use Gmail because I like the interface and the ability to read my email on any browser on any internet-connected computer.
Computer scientists take as a given that everyone worries about privacy. But in fact, outside of computer scientists and a few other techophobes, most people don't. Google not only has my email but also my calendar and if they ever started Google Money, my financials as well. Nearly every major and most minor transactions I make leave an electronic trace. With the right passwords on the Internet you can see what products I buy, what books I read, what movies I rent. So what?
Best as I can tell worries about privacy come from an inflated notion of self-worth. In reality nobody really cares about your private information. The safeguards we have against privacy, while far from completely secure, are enough to deter people for looking for information that just isn't that valuable. Damage will come from people writing in the open; Something someone is writing in their Myspace account today will come back to haunt them thirty years from now when they run for public office.
I do worry about my information online. I worry that people will could delete my files, assume my identity or steal my assets. However I have the ultimate protection against privacy concerns: If you look very carefully at my email, my calendar, the web pages I visit and the stuff that I buy, you'll truly discover that I'm just a really boring person.