Steal this idea: Musical intersections

Listening to you,
I get the music.
Gazing at you,
I get the heat.
Following you,
I climb the mountains.
I get excitement at your feet.
-- The Who, "We're Not Gonna Take It"

There are a couple times when two or more people want to listen to some form of streaming music (road/train trip, shared office space, etc.). Streaming radio sites like Pandora should have the option of combining multiple peoples' musical taste and come up with music that both people would like. Being able to generate a road trip playlist for portable music players would be nice too, though there are the obvious copyright issues.

I imagine coming up with good shared playlists is trickier than just taking the intersection of the songs/musical features. Ultimately, it would depend on the model of listeners tastes. Of course, in many cases, these intersections can be small (my freshman year college roommate and I both liked Stevie Wonder but had little else in common musically).