The statistics on mining now show that it is quite unprofitable - http://blockchain.info/stats Even if those figures are taken with a grain of salt, its clearly not the profit machine it once was.
Given that running a mining rig is becoming less and less profitable, won't we end up in a situation where the only people running rigs are the ones that have a vested interest in keeping the technology going... Probably reducing the total size of the network down to a small group of collectives. Even worse will be when there are no new coins being mined, profitability will be reduced even further - and the mining difficulty will be massive given all the dedicated mining rigs in the market from the boom time.
I jumped on the bandwagon early this year and speculated, gambled, purchased and ended up cashing out before the issues with Liberty Reserve arose and caused issues with my ability to deposit/withdraw from MtGox. So I have spent quite a bit of time using the technology, but have been out of the loop for a few months now.