You can put this in the "Tough to be FEMA" category of issues they have to deal with.
See the Emergency Management Magazine story Outdated Data Places Homeowners in Flood Zones which speaks to issues that homeowners are having with their personal property being incorrectly placed in flood zones.
Anyone who has worked with GIS or digital mapping will tell you that "just merging" data systems with no human intervention and checking does not work. Thus, you have the errors that are being propagated by two data systems that don't mesh.
I see the real issue is in screwing with people's lives and finances. These mistakes cost real money in time and dollars. If the Feds had to pay back those costs, etc. they would be more careful.
In reality it is a vendor or series of vendors who have the contract to make these maps. Penalty clauses for errors in their contract would make them much more diligent in their efforts.