I agree, but since you will have to change it, I'm just saying it's not a contract if it changes from one side.

So, e.g.:

- make it more quasi-contractually binding on yourself, in some principled, innovative way: establish a member user group, consult with them before changing it and give them the freedom to publish the minutes of the meeting, or establish some other meaningful cost of changing it

- or just call it "What we mean when we say 'social network'" or something, otherwise it's about as good as "Don't Be Evil".