captcha on post submission

So I have been keeping up with posts around here for a while and the annoying thing is when you get the random ad poster come through.
I don’t know if its a bot that is doing it or a really really bored person but would it be too hard to add a captcha confirmation upon post and reply submission? that seems like it quells the spam beast a little more than not having one.

more and more spam coming in now. any luck on implementing a captcha like option?