You've probably seen Google bug you about their new privacy policy (and I bet you mostly ignored it).  In a nutshell, it allows them to collate all data gathered on you, from all their sites, together.

So, if you at least don't want Google correlating your search history with your GMail/Youtube etc, you can opt-out now: https://www.eff.org/deeplinks/2012/02/ho...kes-effect
(if you don't sign into a Google account, you can opt-out here: http://www.google.com/history/optout )

Random 1hr privacy related speech if you're bored:
Source: YouTube




Somewhat related, Microsoft's video to try to take a stab at GMail.  Wouldn't consider MS more, but entertaining take on things:
Source: YouTube