Ezra gives 2 of 3 reasons why 2013 is when a lot of the health care bill is slated to ramp up:
1. Implementation is actually difficult.
2. Postponing implementation is a budget gimmick used to keep the cost artificially low (if you only show expenditures in five years out of a ten year budget window the program will appear cheaper than it really is).
And what Ezra omitted.
3. 2013 is after 2012, an election year. In the event that the reform is unpopular people will not be able to express the dissatisfaction for several more years.
That is sort of an obvious one. When you omit something like that you might as well be on payroll.