Even hot compost doesn't kill them. A study in the Journal of Range Management (Douchette and colleagues, 2001) showed that many seeds pass through CATTLE (talk about HOT composting!) and are still viable, so cattle are actually used to re-seed prairies. Nope, put those weed seeds in the real garbage...OR feed them to your chickens, where the seeds get broken up by grit in the birds' crops. That's what I do!
I just read some weeding tips in the Fine Gardening newsletter... Apparently it takes several hours at 180'F to kill most weed seeds. That's hotter than the inside of a cow. A good "hot" compost pile can get that hot, but it can be tricky to manage. They suggested letting a pile of weeds start rotting, drying, etc. until the volume is much less, then putting into a container that you can cover with black plastic for "solarizing" (the sun's heat should get it to 180 in summer) or doing small batches in an old crockpot (!!) out in the garden.
I think I'm going to stick with throwing away any bad boys.