Nothing wrong with this business model...
Dadz is right: yields will never exactly match market demands so some parts have to be sold as lower-end products (less cache, fewer cores, no HT, lower speeds...). If there's a simple way to get back that latent capacity, that's fine. If you don't want it, don't use it: I'm not sure I would.
And regarding Will's comment on the lifespan of processors, in my experience they're never the first, second or third thing to fail in a PC (my cack-handed attempts at overclocking excluded).