From Grant Wahl's piece linked to above:
Here's how it would work: The six lowest-ranked teams in the region would have a home-and-home playoff to trim the field to 32. Then eight groups of four teams would play a six-game quarterfinal stage, with the top two in each group advancing. Then four groups of four would play a six-game semifinal stage, with the top two again advancing. Then two groups of four would play a six-game final stage. The two teams that win those groups would earn bids to World Cup '14. If CONCACAF successfully lobbies FIFA for four spots in Brazil (instead of the previous 3.5), then the two second-place teams would also receive World Cup bids. If it stays at 3.5, then the two second-place teams would have a playoff, with the winner going to Brazil and the loser then playing against a team from another confederation for a World Cup spot (last time it was the fifth-place team from South America's CONMEBOL).
Since the US and Mexico are easily the top 2 teams in CONCACAF, they will be seeded into opposite halves of the draw, only to meet if they both finish 2nd in their pool and CONCACAF doesn't successfully lobby for a 4th bid to the World Cup.
Why do it? Aocording to Wahl, it's so the smaller countries of CONCACAF, many of whom don't have a prayer of qualifying, get more games before being eliminated (for the the qualifying procedures of CONCACAF for the 2010 World Cup, see here). As you can see from the link, 23 of the 35 teams play 2 or 4 games and are then out. Only the top 12 teams play more than that.
Under the new procedures, 32 of the 35 teams will play at least 6 games, with at least 2 of those being against one of the powers in the region (which should help sell tickets for some of the smaller countries).
The upshot? That day US Soccer fans have been hoping for, when the US finally wins an important game in Mexico? Won't happen, as the US won't get the chance to play an important game in Mexico under this format. It's sacrificing the quality of competition for the 3 or 4 teams who eventually make it to the World Cup in favor of the multitude of teams who will not qualify. CONCACAF is already lacking in terms of competing on the World stage, and part of that is a lack of pressure opportunities against quality opponents. Now those opportunities have gotten even slimmer, which should only help to weaken the conference's standing on the largest stage.
In Wahl's article, CONCACAF general secretary Chuck Blazer remarks,
The goal [of World Cup qualifying] is not to try to find a champion of CONCACAF. That's what we have the Gold Cup for...
This is true, there isn't any benefit in terms of World Cup seeding for your standing in your conference's qualification, only whether you qualified or not. But the goal for CONCACAF should be to improve the chances of the qualifying teams at the World Cup, but since a minority of the region's 35 teams have any shot of making it to the World Cup, that's not a goal that a majority of the region will embrace.
This is a dark day for American (and Mexican, for that mater) soccer. Hopefully US silence on this issue at least helps America win their bid to host either the 2018 or 2022 World Cup.