Many sites on the Internet currently suffer from an immense supply of incredibly stupid comments. Some of them are lame and without coherent point, some are whiny jocky-ing for attention, and some are deliberate trolls planted out of some deranged comedic sociopathy (read: they're deliberately pissing people off because they find it funny). Most websites deploy moderators to try and clean up the comments so that they're at least mostly readable, or have some sort of ranking system so that the crap falls to the bottom.
Enter the Stupid Filter. The stupid filter takes a string of text, ranks it from 1 to 5 on "stupid-ness," and passes this on for further processing. Websites can use this "stupid" rating to, say, auto-delete all postings above 4, and write a snide letter to their authors. A stupid ranking of 3 would merit a warning, perhaps.
The stupid filter could be used in many ways, since it merely categorizes based on comparisons to writings that other people found to be stupid. Stupid posts may be automatically disemvoweled, rendering it technically readable but easily skipped, or perhaps on forums, stupid ranking text could be proceeded by a big red "warning, written by a moron" text, such as this:
<------ WARNING: IDIOT
I especially like the forum idea, because having the concept of idiocy directed at your personal avatar might just encourage people to try to avoid spewing this crap. Moreso if it comes with a big fat warning before posting. One would click the post button, only to be shown a warning screen explaing: "Caution, your post registers over the threshold of stupidity! Are you sure you want to make a complete fool of yourself?"
Although knowing how people are, yes, they will make fools of themselves and then complain about how the filters are biased against them. Or they will claim that it is "ironic," since the filter is a computer program and can't tell the difference.