I think that changing the name of a thread in this particular way is misleading and shouldn't be allowed.

But it's consistent with this site's treatment of polls. I once answered a poll and found that the content of the poll had been changed so much that I was on the opposite side of the question that I voted for.

This would be useful for some purposes; you could have a poll about loving the N900 and change it to iPad Fan Club. But I don't think it should be allowed.