I don't know if there is anyone out there who actually gets a lot of traffic from searches that includes the exclusion operator, but it just occured to me there is a rather simple (and unethical) way to get a top listing for such a search.
I'm sure everyone has heard by now about the 'more evil than satan' and other types of searches that produce results which don't actually contain any of the words on the page. While that was fun there is a more problematic side to this, the use of anchor text to drop your competition from searches which use exclusion.
Fore example, searching for Linux OR Microsoft will put the microsoft page at the top. However if you search for Linux OR Microsoft -bugs, you'll notice that the Microsoft page disappears from the SERPS. -evil and -satan give the same result. Some microsoft pages are still in the SERPS, but the main page disappears.
So, your site is in an industry which has common keywords with another industry? You get quite a bit of traffic from searches with the '-' operator? You aren't ranked at 1 for those searches? Simple solution: create a few pages which link to your competitors with the exclusion keywords in the anchor text. Pretty soon you are at the top, and all the other relevant results are no longer there.
What percentage of the general public use operators at all? I don't see much use of it in my log files. I suspect that many users just scroll down through screens of irrelevant information till they arrive at something that interests them. If you are looking for widgets in Mexico the serps will be dominated by widgets in New Mexico unless you use -new. In theory reverse googlebombing could work but I suspect that the -widget searchers are an insignificant number ouside of the webmaster/SEO community.
often i use exclusion queries to remove unwanted entries from a not that precise term. it works quite well but this is more a search optimisation and sometimes it works well against google bombed entries - not the other way round.