Tons of useful things can grow out of a publicly deployed wiki.
I don't know what context you're operating within, but I find the biggest liability of most wiki projects is disuse and apathy, and perhaps spam.
Since it's so simple to set up a pbwiki, or a mediawiki installation (or some other option), the downside strikes me as rather limited. (although that depends on what kind of work or coordination you're hoping will take place on the wiki.)
Does anyone have a link to a resource that compares the features of different kinds of wiki platforms?