Because a lof of the current dividends is derived from hardware sales, which is a short-term opportunity, the real yield, taking into account the reduced hardware sales over time plus the reinvestment needed for hardware sale plus the halving effect, is far, far lower than you currently see.
Why do you say hardware sales is a short-term opportunity?
I would say it's the other way around. Income from mining will not go much above what it is currently, because of the 51% issue. Income from selling mining hardware is still far from saturated. People are bidding up USB miners to +$400
on eBay! The demand is
huge and I think it would be a lot more profitable for shareholders if ASICMiner were to focus more on hardware sales now when there is such a large demand to satisfy.