I'm a landlord and "pre-screen" my potential tenants through Google searches. I am constantly amazed by photos, comments, and other personal information I find. Sometimes that information means I won't be returning your phone calls/emails.
Edited: I just wanted to add to the paranoia... with a recent legal case in LA where a lawyer downloaded EVERY picture in a Flickr account to use as evidence AGAINST this person. While in "real life" this person is extremely responsible, the photos gave the appearance of a reckless attitude and provided evidence that they "condoned" illegal activities.
The internet is a scary place and anything you post is permanent, regardless of your attempts to "erase" it.