Pasky: I've always wondered about the largest capture in a pro game and especially the largest seki that ever appeared.
There's a game by Jowa (white) vs Genan Inseki in which more than 150 stones are captured. It's 1814-10-23a.sgf in the GoGoD database, and I think it's mentioned elsewhere on this site (although I can't seem to find it right now).
I believe the Jowa game is here http://senseis.xmp.net/?RetrogradeAnalysisProblem1.
The gogod's new in go site has an article about sekis too.
http://www.gogod.demon.co.uk/NewInGo/NewInGo.htm
Wow, I really am having a bad go day... I looked at the page and was stumped, so I went to the attempts page... and it turns out that *I'm* the one that made the attempts page and gave the correct answer! hehehe