I was in Home Depot today and there was a guy there doing a Dremel demonstration. Since I saw a recent thread on the cost of replacement blades for Fein tools, I asked him about using Dremel blades on Fein tool's oscillating cutter. According to him, the Dremel cutter will fit the Fein tool but not the reverse. When I asked how the reverse was not true, he stated they were designed that way.
I can't corroborate any of what he said since he was just ending the demo, but I thought if true, it would be a good thing to know considering associated Fein blade costs.