I'm actually going to agree with Brian in the sense that, if getting a lot of viewers is important to you, then you're just going to frustrate yourself by streaming when nobody shows up. Frankly, there's only one guy (Allen) who gets consistent, guaranteed viewers. And anybody who watches Allen knows why!
Many of us don't really care how many are watching, or whether anybody is watching at all, we just stream our gameplay because "why not?" I lean toward that category. I rarely stream, simply because it's slightly more of a hassle to do so than not to, and I can't be quite as relaxed. When I DO turn on the stream, it's mostly just to see if anybody wants to chat. I couldn't care less about having my gameplay watched.
But some people DO want an audience, and it isn't worth it for them to play without one. To each his own.