Depends on the situation, I guess... normally I chase alone or with one partner. It all depends on how long I'll be gone. I love chasing in a caravan of chasers, and had the chance many times in 2004 to do so. When I'm chasing Eastern Colorado from Denver (an afternoon thing), I usually venture out on my own, perhaps running into someone along the way. In any case, I usually chase solo in my own vehicle and in a caravan of other chasers along the way.
I have partnered up with people on extended chases. My girlfriend has accompanied me on afternoon chases in Eastern Colorado as well as two day trips as far as eastern Kansas. She, too, usually finds ways to pass the time when things aren't in urgent mode, but she's great company.
Basically, I love chasing in a caravan of chasers, and usually prefer to keep it that way! 8)