They are interesting but they are a little different in that they are really just consolidating group buys. If they increase their hashing power, they will sell more shares, so there is no possibility of increasing your dividend without buying more shares. We are doing it a little differently in that every shareholder gets an undiluted piece of the pie, as we buy more machines, your dividend could increase without ever investing more Bitcoin.
Without knowing future difficulty it's impossible to say that dividends will always increase. With reinvestment (either DRIP, manual purchase of additional shares, or reinvestment by the security itself) you can increase your stake and total hash speed. Any reinvestment strategy will increase total dividend (sum, not rate) at the expense of greater total investment in the company itself.
