Came across this bit of news: http://www.sigmaphoto.com/news/news.asp?nID=3306
about a lens that Sigma has in prototype. It was shown at PMA as can be seen here: http://www.youtube.com/watch?v=K77UvaiHii0
Looks to be about 3 feet long, maybe more, and I'd hate to guess the weight. The Hassleblad 300mm f/2.8 lens weighs, if memory serves, about eight pounds and this one dwarfs that. Might be nice to hang on the wall, but I can't see a really practical purpose. Even for sports photographers, managing the thing looks like quite a feat!