I think ERP argued about this once, because vertex shaders have to have an exact same number of vertices for input and output - if you point input to some randomly changed memory address, you get just what you need - a free fenerator (ERP, please correct me if I misunderstood this)
Yeah I remember that too (a little debate between ERP and fresh). I believe he also mentioned something along the lines of just reading a random number from a single address as well...
I had wondered how well that would work (and rather curious about how much bus chat that might lead up to). I personally would rather just generate verts from a perlin noise map (more natural looking patterns)...