I am completely onboard with EBarnacle, and doubly with Midchuck.

For me, hearing the word "exposure" from a stranger over the phone elicits pretty much the same response as being asked to play a benefit for the National Association of Child Molesters (and bring my own PA) would. OK, slight exaggeration there.

My experience is that anyone who offers "exposure" cannot provide it, because THEY DON'T KNOW WHAT THE HELL THEY'RE DOING!!! And starting with the grand precept that you'll play for free as a convenience to them, you'll be lucky to get a gratis hot dog out of the deal.

So those are the gigs I turn down, cause they're not real gigs.
Not long ago, someone I know who is like Queen of the Mountain in her own head, had one of her proxies call me up and ask to borrow "a small microphone" for their event. I soon figured out that by "a microphone", they meant "a PA system". Honestly didn't know the difference!

Yup, I'll play for a good cause in a heartbeat. To me the definition of a good cause does not include "because we want to have a bunch of music without paying for it", which seems to be the norm for many community events. Later on, though, you find out that sure enough, one or two "headliners" did get paid--in fact, got paid a lot, and there was just no money left for anyone else. This is not a system I want to support.   

And like Max, I don't care for 'vanity gigs' either. Just to be able to say you played there, and leave out the detail that there was no audience? I'd rather catch up on me sleep.

W-O
Funny eh, as I get more jaded, I get offered more & better gigs. Because if you can provide a professional performance--on time, more or less sober, and appropriate to the venue and audience--that will get noticed and will get you the references that will get you your next paying gig.