I see people's point about not having to scroll through all the messages, but I usually find the reasons people give to be more valuable than just the yes/no or this fabric/that fabric answer. I think the conversation is valuable, not just the percentage of people favoring each choice (in whatever the matter is).
Plus sometimes I "know" someone on the board and feel that their opinion is particularly valuable on a particular subject. That sort of thing gets lost in a poll.