occasional gradcafe lurker here, who started an account after reading this topic...
I'll also play the online dating story game. My first semester of grad school (and first semester TA-ing), several of my undergraduate students found my okcupid profile. okcupid lets you see people who have recently viewed your profile - I had a sudden influx of 18-22 year olds living in the town in which my school is located. I didn't click through to any of their profiles, but recognized them all from their pictures. I deleted my profile immediately and haven't created one since (and am somewhat upset about this, as online dating really is a great way to meet new people).
Needless to say, this created quite a few problems. I didn't have anything too scandalous on my profile, but it was (obviously) far more personal and less professional than my demeanor in the classroom. I felt like I lost some amount of authority as an instructor, as these students were clearly trying not to laugh during subsequent classes (and I have no idea how many students in the class they told). One of these students started sending me highly inappropriate emails, which I then had to report - it was a mess.
...bottom line, if you will be TA-ing or interacting with undergraduates, think very hard about whether you want to have an online dating profile - and if you choose to do so, be extremely careful about what you put on your profile. (Seriously, I had little beyond my sexual orientation/gender identity (which did out me as queer to these students - not something I was trying to hide, but something I would have preferred to share in a different way), age, favorite movies, things I like to do, etc. - but that still affected me very negatively)