I actually thought of the idea of selling my blocks at a profit but for a different reason.
Virgin unspent blocks are more anonymous than blocks that were acquired any other way. If I were to go buy BTC from a brick and mortar Bitcoin dealer that "knows your customer" and then I go use it to buy drugs or something, there's a link. Maybe one wouldn't chase it for drugs, but for something more heinous, maybe.
A freshly generated block has absolutely no history...
Sure but, if you can mix them in with coins that have passed through other hands, is that not just as good?
Possibly better, since backwards attacks are possible. Consider this, you buy drugs with btc from a mined address.
Now the rest of your coins, mined from that block, are all tainted with your drug transaction, and can still give you away back to that transactions when you otherwise sell them.
Maybe you worry less about this? Maybe not? In any case:
https://en.bitcoin.it/wiki/AnonymityIs an excellent link