I don't see it as an issue. Like others have said, you probably already use the same password across different Google systems already, so there was a risk before. You could have chosen other sites/apps to use, but found the Google ones to fit your needs.
I guess those people out there that search for things on Google like "busty babes" may or may not want that showing up on their YouTube main page (for those trying to hide it from their significant others). Then again, either stop, or search using something besides Google if you don't want the results tracked.
Not a big deal and should actually make things easier in the future. Heck, Apple and Microsoft gather so much data from us already and we've been OK with that. The super popular iTunes likes to hijack all of your music and video stuff and can somewhat force itself upon you, but we say it is OK.
I'm not concerned, and I am usually a skeptic about this kind of stuff.
