Let's get this out there first and foremost: I have no interest in tracking applicants down online. I have no interest in reading their feeds, seeing their pictures, or gauging their interest based on online content.
My old philosophy about social media was that it was the students' domain and we should stay out of it. I've changed my stance over time, though. Now, I figure that I should provide students with as many easy ways to contact me as possible so they can get questions answered. So, I'm on Facebook, Twitter, Ning (rarely), instant messengers (on deadline nights), and the blog. The important aspect of my presences is that I'm not searching students out. They decide how they want to get in touch with me. The contact is on their terms.
If you want to make up an alias and comment daily, that's great. If you never talk to me using these vehicles, that's fine, too.
EDIT: I should add that I post something like this each year, just to restate my position on the issue. I gave an interview to USA Today about this last week and the resulting article spawned similar pieces by Reuters (with quotes from my interview, interestingly) and CBS.