I'm either being judged for my dancing or judging others in my field. Even when I'm out at a club, I skim the crowd to see who catches my eye.
Group A: Most lone dancers tend to dance their best when they don't violate the "fourth wall." These include drunk dancers "in the zone," tired dancers, guys who are pissed or elated about something, guys with a little substance enhancement, or people on the edge of psychosis. In most of these cases, the dancer tunes the rest of the world out and play-acts their fantasies or emotional states.
Group B: Some dancers are best when they're cognizant of the audience/crowd, and use the audience as a springboard for inspiration. These dancers tend to be highly trained or highly evolved and turn it up when they're being watched. They may make eye contact or strategically avoid it while projecting their dance toward a person or group. Rarely are they in a precarious or anti-social emotional state while dancing.
Once in awhile I'm in group A, but as soon as I start moving, I usually slip into group B because it feels like home to me. Most of the time I'm in group C, the watcher group.