Chris Lott coined the term 'creepy treehouse', and John Krutsch defines it as "a place online that adults built with the intention of luring kids in." Jared Stein has an excellent post on defining a creepy treehouse further:
n. Any institutionally-created, operated, or controlled environment in which participants are lured in either by mimicking pre-existing open or naturally formed environments, or by force, through a system of punishments or rewards.
n. Any system or environment that repulses a target user due to it’s closeness to or representation of an oppressive or overbearing institution.
n. A situation in which an authority figure or an institutional power forces those below him/her into social or quasi-social situations.
None of these commentators is suggesting that we shouldn't exploit new technologies for learning, but rather warning of the way in which you do it, to avoid Creepy Treehouse Syndrome.
I think it's an excellent term, but I have a couple of reservations about it. Firstly, it could be used as a justification for not engaging with any social networking tools in education. You can imagine someone saying 'I've heard students think you're building some kind of creepy treehouse if you go near that stuff. What they want from us is distance, authority and lectures.'
Secondly, it suggests that all learners are young (I know that is explicit in the definition of luring kids in, but it could be extended to all uses of social networking in education). In the States and many other countries the number of higher education students older than the traditional 18-22 year old range now exceeds those in that range. There may well be different needs and different uses of technology for the adult learner. They don't see it as a creepy treehouse, or even a happy playground, because those are not meaningful metaphors. These are people more concerned with a peer or a professional network.
For instance, I asked all my post-grad students to sign up for Twitter. Some have stuck with it, some haven't, but for me it has changed the dynamics of that educator/student relationship and made it more peer like. I was pleased to see that one of my students, Manish, is now doing the same with his students. I don't see anything creepy about this (of course, the students may disagree!), because of the different nature of learners involved.