Geographic definitions can be a highly political topic, and this is the case when talking about what constitutes Europe. The disagreements on regional boundaries extend beyond the lines themselves to include disagreements over what factors should determine the lines -- physical features of the land, cultural similarities and differences, political agreements. We could talk for months and not reach a consensus (and if we ever got close to agreement within a certain set of facts I'd guess enough time would have passed that the underlying cultural and political determinants would probably have changed).
This conversation is getting carried into an area that is divisive, and really outside the scope of this forum. I would say people should categorize themselves for the poll in the manner they would typically identify.