GN, you're absolutely right.
A quick word from the employer's perspective...
In my work, I'm often in the position of being a hiring manager. The staff I hire deal with sensitive, confidential information, and in some cases work directly with clients.
I do a Google search on all short-list candidates, and if any social networking stuff comes up on the Google search, I check it out.
It's definitely something to think about. Everything you do on the internet leaves a trail. You can mask things, but almost nothing can ever really be deleted.
Trinity