Anyone hooked more than one reciever to a hub?

Yes. It works fine. Assuming an MP3 bitrate of 128Kbps, and a hub bandwidth of 10Mbps, you can ideally get 10,000/128 = 78 streams at once. Obviously, this doesn't count collisions, overhead, etc., so we'll assume half-duplex transmission (so 5Mbps), 40% efficiency and overhead.

This comes out at 15 streams. If you've got a hub with more than 8 ports, I'd be surprised.