-The first guys that get a crack at entering is the 10 person Gold Group. That currently consists of top 3 at 2008 Olympics and Top 7 from 2011 WTS Series. 7 of those 10 guys took their spots (Alistair Brownlee, Brukhankov and Vidal passed).
Then next they take 30 guys from the current WTS standings. (so just Yokohama in this case). Its important to note that they take 30 guys and not necessarily the top 30. Because some from this ranking already are included in the Gold Group or chose to pass their spot, those spots get rolled down. In this case you had to be in the top 35 to be included. This is how Chrabot, Shoemaker and Fretta got in. (Fretta finished 32nd but was the 25th included because of roll downs)
Next they take 20 guys from the ITU points list that aren't already qualified. Manny Huerta was the 20th of 20 to qualify this way. He was 43rd overall on the points list.
So if you've been doing the math there are 7+30+20 guys that have taken a spot already. Now they continue down the points list until they've reached their predetermined field size. In this case they happen to choose 65. So they took the next 8 available guys on the start list to get to 65 total starters. The last guy let in was Clark Ellice of NZL who is ranked 56th on the points list. Ethan Brown is 58th and Greg Billington 64th.
Next up USAT has their own qualification specifications. Each federation is given the opportunity to sub out one racer for another. So USAT has created their own list which takes an athlete's two best scores from post Grand Finale WTS, WC or Continental Championships. That substitution is automatic unless the one being subbed out is protected (yes another list). In this case Mark Fretta will be subbed out for Hunter Kemper who is the highest unqualified athlete on the USAT record. If Kemper, is not healthy that spot will be rolled down to Greg Billington who is the next highest.
Interesting to note- Sarah Haskins will be subbed out of San Diego. The third women's spot was largely believed to be a toss up between Haskins and Laura Bennett. However, Haskins (who has spent the majority of 2011 racing non-drafting) will be subbed for Jillian Peterson, who has a higher USAT ranking.
Moving on, ITU also reserves the right to give up to 5 discretionary invites. There is also the matter of withdrawals which will get rolled down on the points list. So that gives Brown, Billington,Collins and Fretta some hope to make it. Accounting for the fact no federation (asides from the US as the host nation) can have more than 6 entries, Brown is 2nd on the waiting list, Billington 7th and Collins 11th. Of course though, if they gain entry they would have to be accepted by USAT's policy as well.
If you want my projection of which Americans will actually start at San Diego, well I have no freaking clue. This process is super overly complicated