FranticFish - 7:42 pm on Nov 8, 2010 (gmt 0)
I've tried this so far with one site for a household name in the industry and I had no better response from my 'while you're fixing these how about adding mine?' emails than I did to my 'gimme a link because its X's site' emails. I will do it again but the vast majority of emails weren't acknowledged even. I'd definitely do it again though, and I'd bet the success rate is higher if you have a page that is offering the missing information being linked to rather than just a site in the same niche.