Why are all the cons in Dallas?
In a large part, this is due to Meri Davis (ne Hazelwood), who started Project A-Kon almost 20 years ago.* There used to be two types of con organizers...those who where into for the money (dangle the guests out, fleece the attendees) and those who went broke because their hearts were in the right place, but they had no real business sense.
Meri changed that. Not only did she put together a con for the fans, by the fans, but she taught others how to do it as well, and assisted them. As such, several wonderful cons of various flavors have popped up around Dallas that import people from all over the world (some of them comprised of a combination of Aggiecon folks, Meri's minions, and ORAC members...who often fit into both the other groups. ORAC is an old, almost died 3 times over fan group in Dallas that predates Meri's efforts).
Also, remember, Dallas is responsible for Doctor Who being in the US in the first place...their PBS was the first to pull the show over, long ago.
And it has better weather. Our weather sucks down here. Hell, even on a good day, we're still 33 feet above sea level. Drive up to Dallas, you'll be able to breathe better just north of Centerville.
*Dear god. 20 years?
