Remember how Obama said that 46 million Americans were uninsured and that the ACA was needed for them. He talked about how they were asking for this bill to be passed:
"We are not a nation that accepts nearly 46 million uninsured men, women and children" - Obama, June 2009
"Nearly 46 million Americans don't have health insurance coverage today" - Obama, August 2009
Of course, we all know that he revised that in Sept of 2010 - "We are the only democracy—the only advanced democracy on Earth—the only wealthy nation—that allows such hardship for millions of its people. There are now more than 30 million American citizens who cannot get coverage." - due to his initial counting of illegal aliens in his initial number.
So, the CBO estimated that 7 million Americans needed to sign up and pay up by Mar 31, 2014, on the federal exchange to make their numbers. So far, with only days left to sign up, we are at 4.2 million signed up, and the administration is not saying how many actually have paid for their selected plan - you know, actually have enrolled.
Administration: 4.2 million people signed up for Obamacare plans through February - Kyle Cheney - POLITICO.com
Selecting a plan is the equivalent of test driving a car - it means nothing until you sign the contract to pay for it. Obamacare's numbers are simply test drives, and are not saying how many have "bought the plan" (enrollment). And of those that actually did enroll, it appears that only 80-85% of them have actually paid for it so far.
The real question is - since Obama said that 30 million needed insurance, why aren't they signing up in droves?