I doubt it's illegal, since they were "only" accessing publicly-available information — but manners don't get much worse. And lord knows how they manage to find the time to Google everyone who comes to their meetings! The mind kinda boggles.

OTOH, perhaps they were all always like that, and we just didn't hear about it before?

Someone on a Livejournal group has suggested as much about the Ontario Liberals under McGuinty, that his audiences were vetted, but wasn't able to provide a source for the accusation. Until I see some proof otherwise, I'm operating under the assumption that I would have heard if others had been vetting their crowds in this way.