If you think of it as an entertainment expense, like gambling, or if you like the idea and want to be a part of it even knowing that you probably won't get your money back, then sure, do it.
I wouldn't go quite that far, though the calculus has to change significantly... the cost of your capital is going up, and this will be realized in the 'price' demanded for the good that you produce using the capital, and since it is rising at the same rate for ALL miners, all miners can (and will) demand a price premium in order to continue mining, or will exit the market. As more processing power is required in order to produce the good, a higher premium will be demanded, and if that does not happen, enough miners will quit mining to allow a relative price equilibrium to be established based upon the actual demand for BTC.
What will probably happen as difficulty continues to increase is a bifurcation into hobbyists and professional miners, plus some oligopoly-type action when one or more of the larger pools start to exercise its market power, and as more and more independents are forced to join the pools. This whole thing is like a business school case study!
There are certainly stupider ways to make money