OK, it’s a phrase, not a word. But I’d not heard of it until Howard Rheingold mentioned it in a tweet. Flexknowlogy has a short essay describing various ways the phrase is used. Here’s one that is important for college professors (and the reason Howard was tweeting):
n. A situation in which an authority figure or an institutional power forces those below him/her into social or quasi-social situations.
With respect to education, Utah Valley University student Tyrel Kelsey describes, “creepy treehouse is what a professor can create by requiring his students to interact with him on a medium other than the class room tools. [E.g.] requiring students to follow him/her on peer networking sites such as Twitter or Facebook.”