Well while I understand the reasons the gliders dont want to have a transponder on it makes no sense whe you look at modern avionic power requirements. South of Reno many gliders work out of Minden in the summer with no transponder at up to FL180. We have many near hits every year. There is a lot of high speed jet traffic decending and climbing through the area. About 18 months ago we had a mid air between a Hawker and glider. The glider even had a transponder but did not have it turned on.
http://jeremy.zawodny.com/blog/archives/007288.html
There is no way a jet at 350mph is going to see a white glider visually everytime.