@rancid I, like richardhenry, cannot speak for Andrew or Ben, but I do remember having conversations with Andrew way back in the days when Fluther was barely a twinkle in their eyes. Andrew and Ben were friends from college and had collaborated on several successful and, I would imagine, rewarding projects, both technical and artistic in nature. I would guess that there was a significant appeal in working together to launch their own web start-up.
As to the specifics of Fluther, I believe the inspiration came from the SUN lab at Brown University, where students would, through a shared network, help each other with random and not so random problems on assignments and projects.
And yes, I do think that they hope to turn a profit from this venture. Nothing wrong with that.