But, if it's a really good idea, wouldn't you want to keep it to yourself as opposed to throwing it at other people so they can butcher it for you?

if you really love the bunny, you will love it enough to let an abler (ie less busy) plot!mummy write it. ;)

i think there is a definite difference between occasionally having a really good idea you're too busy to write and taking a massive hyperbolic brain dump in the middle of an unsuspecting comm, though. posts like the ones you're describing are a big reason why i don't have much to do with fic these days...but i can more than relate to someone going, 'shit, i've worked on this idea and tried to finish it but other stuff keeps coming up...but damn, i'd still love to read that story.'