The problem I can see is that I expect the option "I would attend Maemo Summit 2010 if it was held in Canada" is read by many to imply that they wouldn't attend the Maemo Summit if it wasn't held in Canada.

This is the problem with polling like this: it can't be indicative because it doesn't capture nuances like "I'd probably attend the summit if it was in Canada, but I'd prefer it wasn't. I haven't looked at flight details - it'd depend on the time of year as to the cost - and that might be the deciding factor."