Some five years on, the story still holds up.

The Sons of Ben painstakingly built a groundswell of support for the Major League Soccer franchise they envisioned in their home of Philadelphia, growing from a handful to a few thousand in the process, convinced a group of aspiring owners that there was a market, petitioned local politicians for stadium funding, and finally got MLS to award them a franchise. And as their payoff, they got not just a team but also input on the design of the stadium's supporters section and even their own gate.

"Sons of Ben: The Movie," released this summer and now available on DVD, offers a timely reminder of this unlikely tale. It's a deeply reported and honest look at the long and winding process of building the supporters group and then the club, but also the absence of the promised development in the area. It's a well-made and really enjoyable film on the most unlikely story of genesis in stateside pro sports.

But it's also a history lesson, harkening back to the most fevered period of expansion in the league's history, when it added teams in four consecutive seasons. Drawing from the game plan of Toronto FC's very successful admission to MLS in 2007, the league decided to bring on more teams with pre-existing and well-established fan bases. So the Seattle Sounders joined in 2009, the Philadelphia Union in 2010 (thanks in large part to the Sons of Ben), the Portland Timbers and Vancouver Whitecaps in 2011, and the Montreal Impact in 2012.

All of those expansions proved wildly successful – commercially at least – with all of those teams drawing large crowds that finally helped to accelerate the league's tortuous attendance climb. After MLS had some misfires with the markets it chose in its early years (although some teams were eventually turned around), this blueprint has proven failsafe. All of those places have held up as strong soccer cities. Only Montreal has seen its attendance slip steadily, perhaps as a consequence of its futility.

Of the league's latest additions, Orlando City and New York City FC have also done brisk business. Orlando was an existing club with an eager fan base, so that was little surprise. NYCFC stepped into such a large market, rich in 20-somethings with worldly tastes and disposable incomes, that its success was practically assured as well.

But in choosing the four teams already announced to be joining MLS and boosting its numbers to 24, the league hasn't exactly fallen in line with its own hard-won philosophy.

LAFC, scheduled to begin play in 2018, will rise from the carcass of the failed Chivas USA experiment. And while Los Angeles, too, should easily be able to support a second team, there is no demonstrable appetite for more soccer there.

Atlanta, a 2017 addition, is a major metropolis without any guarantees that pro soccer will find an audience there. And that's not to mention that it will play in an NFL venue permanently, a bad habit that MLS had seemingly kicked years ago.

David Beckham's as yet unnamed team in Miami – we'll call them the Miami Whatevers – has no slated start date because it still has no stadium deal in place. It will step into a sports market notable only for its apathy, and for having already failed as an MLS town – albeit in neighboring Fort Lauderdale.

Minnesota United – joining in 2017 or 2018 – will operate in a region that's hardly a soccer hotbed, even though the club has built a respectable attendance down in the North American Soccer League, from which it will be elevated. As such, this is seemingly the least risky proposition.

But these are risks all the same, especially for an enterprise that had finally figured out its formula after some two decades of steep losses. Times of overexpansion can hurt leagues very badly – just ask the old NASL. Or even the NHL.

And as the Sons of Ben's story reminds us: The desire for soccer has to come first. Then follows the team.

Leander Schaerlaeckens is a soccer columnist for Yahoo Sports. Follow him on Twitter @LeanderAlphabet.