Posted: 20/04/2012 at 18:04
Yes, that happens with my feeder, too, and that does have a tray underneath. It catches quite a lot of the seed, but much more falls to the ground and it does germinate and have to be weeded regularly. 
I don't know if the seed could be re-used as it were, and it is an expensive waste. However, on the plus side, at this moment I'm looking at three siskins and two goldfinches eating happily.