The only conference I've gone to for the past few years is Netroots Nation. I like the conference but am on the fence about this year. I wanted to talk about Donate Your Account but I've missed the deadline. It also wasn't clear that I could even apply to speak without some sort of nomination.
I think people decide they are either going to go to a conference like Netroots Nation or not go. I don't think they decide based on a perfect schedule of sessions that meet their requirements. You know who is probably going to speak because they speak every year.