First of all, I realize that the subject is a bit ambiguous, since it seems that Jesse has taken full control of the front page at the moment. But I'm referring to his article on the MLS in northeast Ohio.
Let me start by saying that I was a HUGE Cleveland Force fan back in the day. They are the only team for which I ever held season tickets. Their rivalry with the Baltimore Blast was a big and real to me as Browns/Steelers. So I well remember the packed Coliseum for many of their games.
That said, I think Jesse misses a couple of points when using the Force's run of success as evidence that the MLS can succeed in NE Ohio. First, we have to remember what the Cleveland sports scene looked like in the early 80's, when the Force started to gain a following. It was bleak. Now is a friggin paradise compared to the early 80's. Back then, the Cavaliers were firmly in the grip of Stephien, the Indians had not been a contender in a few decades, and the Browns had been mediocre to bad for about a decade (minus the Kardiac Kids year). In short, the city was desperate for a winning team -- and the Force, though never the best in the league -- was that. So a large fraction of those who ventured out to see a game for the first time were probably drawn by the chance to see a home team that was at least competent at its game. Now that the Cavs are about as successful as the Force was then, that drive won't be there. It's not a coincidence that the Force's decline started right about the time Bernie Kosar started taking snaps for the Browns.
Second, indoor and outdoor soccer are two very different games. For one thing, 6-4 was a pretty typical MISL score, not 2-1 as in the MLS. The indoor game is much faster paced, owing as much to hockey (there are line changes and a penalty box!) and basketball in its tactics as it does to outdoor soccer. While I can certainly appreciate an outdoor game played at a high level, I've never become remotely as interested in it as I was in the MISL.
I'm not saying that the MLS can't succeed here, and Jesse makes good points about the demographics and location of potential fans. I'm just saying that using the rather unique run in the 80's as proof is a bit shaky.

stay in the league where you can compete year in year out --- works.