As in implementable in a couple of hundred lines of JavaScript. If I had good answers for the second question, I'd be a lot more sure than 20%.
Something that disqualifies things that don't contain keywords from the thing you're currently working on might function as a very crude version of this.
Come up with 20 independent algorithms like that, use bayes theorem to combine the results, and you should come pretty close.
I was very interested in the discussions and opinions that grew out of the last time this was played, but find digging through 800+ comments for a new game to start on the same thread annoying. I also don't want this game ruined by a potential sock puppet (whom ever it may be). So here's a non-sockpuppetiered Irrationality Game, if there's still interest. If there isn't, downvote to oblivion!
The original rules:
Enjoy!