Compete admits bug, says they'll recount
[Update: Compete ups stats: Y! up from 13.3% to 19%]
Steve from Compete has posted a comment confirming that their regex did have the bug pointed out by me. He, however, added that for capturing clicks on result pages, they use other regexes which don't have such a bug. He assured that they'll do a recount and update their numbers. I don't know how much difference it'll make to search engine market share numbers. But, any increase will do good for Yahoo!, I suppose.