I'm with you on this one.
I'm trying to develop some cheap blue-casting units (the ones I see for sale start at about $300US, and there's no way a NiCad battery, cheap processor, 64mb of memory and a bluetooth dongle cost that much or should be the size of a hardcover book!)
because I've noticed the vast majority of people are stupid enough to leave their bluetooth on discoverable mode.
Seriously, if you can get a small blue-caster, load it up with something, and drop it off in the local shopping mall in bot plant or something. You'll get hundreds of hits on the damn thing!
Maybe hang around, make sure no one spots it. Maybe just wander the mall the whole day with it in a backpack.