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If you can think of a way to abuse posting privileges, you can think of a way to abuse polling privileges. It's just one more tool of the basic post.
my point is, why do things the hard way when there is an alternative to do them the easy way.
Seriously though, this isn't a permanent choice. I still agree with MP, but why not try it out? We could argue over possibilities forever, but a trial will solve it. If it isn't abused, a great new feature is gained. If it is abused (which a few may regardless), impose penalties. If it is widely or even semi-moderately abused, turn it back off. Very little harm done.
Extremely desirable, extremely usable. There are many, many polls out already. Enabling this feature simply allows for easier tallying of said polls.