I don't understand why more people don't just get up and leave. Yeah, it can be perceived as being rude, but I view someone bait and switching me to listen to a 45 min sales pitch as rude. If the majority of people did this presenters/conference planners would get the point.
I DO realize that some of these pay the bills so I give them 10 mins tops. If you don't start talking about meat-and-potatoes after that, I'm outta there.