You could almost think of it as the MLC part being discounted for it's lesser reliability. There are a few good systems for counteracting that lesser reliabilit

You could almost think of it as the MLC part being discounted for it's lesser reliability. There are a few good systems for counteracting that lesser reliability, but fundamentally, you're right - it's just another subset of failure points you're introducing. There are some interesting options for counteracting the higher MLC failure rates - Yu Cai and the VLSI Design Group at Carnegie Mellon have produced some pretty interesting work hashing out the problems with MLC Flash and how to counteract them. For example: the in-place reprogram they've suggested would really help counteract retention errors in MLC, which are the most frequent kinds of errors in that medium.