Depends on the map of course, but usually at least 5-8 other guys.
Quake is a sacred thing to be shared between two people.
Quake is best played with 63 people all trying to find the 64th guy who's holding the chicken. I keep my taunts reserved for Mario Kart, when I can see my opponent. Everyone likes to talk the smack. You can't shut me up. ICQ are my two leading social outlets.