Things that stop me:
A) Remaining shreds of dignity. (Oh, c'mon, I've done sketchbook commissions at furry conventions. What am I clinging to?)
B) Time is money, and time spent on writing with no potential use is arguably wasted. (Am I not allowed to do stuff for fun any more, brain?)
C) Ethics. (Heh, heh, heh. No, really.)
D) Granted the breadth of the readership and the odd places you find them, and their beady little perceptive eyes and the fact that someone would undoubtedly take it on themselves to play scavenger hunt and go find it and the perhaps regrettable distinctiveness I've been told my writing has, the odds of someone NOT finding it eventually, probably in a shockingly short period of time, thereby potentially revealing your dreadful shame to the internet as a whole... (And we have a winner!)
I am starting to think that fan fiction vaccinations might be a good thing to offer.