We already know that up to 1/3rd of all Exchange enrollments have corrupted data (ignoring Jay Carney's non-denial). It looks like Medicaid enrollments have similar issues. From Wonkblog:
Every week, usually on Tuesday, the Centers for Medicare & Medicaid Services sends state Medicaid departments something called a "flat file."
These files are sort of similar to the much-discussed 834 transmissions, which the exchange sends to an insurance plan when someone signs up. Except the flat files are for the Medicaid program, and lists people that the exchange thinks -- but hasn't officially determined -- will be eligible for the Medicaid program.
And, much like the those 834 transmissions, Medicaid officials say, these flat files are riddled with errors and incomplete information.
"They are really incomplete with lots of data cells missing," said Matt Salo, who runs the National Association of Medicaid Directors. "Sometimes the immigration status is missing, or their town is in a different state. A quick glance sometimes shows they're not Medicaid eligible because they earn too much, or they're already in the system."
The flat file was not initially meant to be an enrollment document. It was meant, instead, to give states a sense of enrollment volume, so they could beef up their staffing, if necessary. A separate account transfer function was supposed to be the actual enrollment vehicle.
That separate account transfer function, however, has not yet gotten off the ground. So the federal government told Medicaid directors Friday that it let states rely on a cleaned-up version of these flat files as an enrollment document.