I can’t think of a situation where I would reference fluther in an essay, but I have listed a similarly forum-based website (devoted to interlinguistic and translation issues) as a source. If I consulted it in writing the paper, I cite it.
Alright, I could perhaps see myself citing fluther if I were writing a paper for a sociology class, and I wanted to discuss a hypothetical situation, if I had gotten the idea of the situation from something on fluther.
I could also definitely see myself citing it for creative endeavors, such as shadling’s question the other day, about “What would a 20-year-old-male say” or something to that effect.