I'd like to think my reasons for getting behind a Boston-con would be totally obvious.
It wouldn't be my top choice, though. With airline prices steadily on the rise, I'd be concerned with Boston turnout. Some obvious folks like myself, Rachel and Shane would be pretty much definite, but I can't imagine we'd see much of any of the further out forumites that are under twenty-five, as it might fall out of their potential price range (As it stands, people like Bryan, Jordan, Ruyi or Yelley would have to drop like $400 for a flight or spend three days each way on a bus. I really don't think any of the forumites out on the west coast would be able to attend (As evidenced by the complete lack of any of them attending Tronnocon).
I think Chicago is probably the optimal destination. It's closer to the west coast, while still being easily accessible for most East coasties (Didn't half the Tronnocon attendies drive through Chicago on their way anyway?). Meanwhile, any Europeans who'd be going at all (I.E.: Tommy) would probably be able to afford the extra distance on a plane. You're also dropping a hundred bucks or so off airfare for any west coasters and putting it in a central location for most of the US residents. Aside from that, there's a higher contingent of east coast adults than west coast adults on this forum. Most of the west coasters are college students who really can't afford to get all that far out, whereas a pretty large contingent of east coasters are at a point in their life where they can afford to make a further trip than some others.
For that matter, even if we wrote off the west coasters, NYC would be a much more practical venue for a meetup. Shane's actually closer to NYC than Boston and both Rachel and I can readily afford a trip out to NYC at the drop of a hat. Meanwhile, Phil, Eugene and Tyler are all routinely out in NYC and there are tons of cheap bus services (Boltbus, Megabus) that service NYC for cheap that more of the close forumites could hit up.
Further down, but also a good point for consideration would be DC. Those of us in the Northeast can get there on the cheap (BoltBus has a charter from Boston to NYC and from NYC to DC) and a few high quality forumites live a short drive from there. It's also not a bad distance for the Great Lakes forumites like Eed, Joe, Linds or Cerny.
As much as I'd love not actually having to take any time off work and not having to book any accommodations to make it, Boston is just horribly impractical for a large scale forumite gathering, in my mind. Most forumites are more than welcome to couch surf at my apartment on any given weekend that I'm home, but anything large scale would a pretty monumental production compared to others.