I am a computer hobbyist, so it is better to have an engaging hobby that pays even a little as compared to a hobby that simply costs.

Furthermore, the setup of a typical mining rig is quite scalable insofar as additional rigs are hardware and software copies of the reference working rig. But suppose that I replace the six obsolete 5770 cards with modern R9 280x cards. One could argue that with bitcoin increasing in price 10x per year, the funds spent on a mining farm scale-out could be better invested in simply buying coin. I expect that I will incrementally upgrade my rigs.

Another concern is that ASIC rigs will be available sometime this year for scrypt-altcoin, e.g. Litecoin, mining. I am not too worried about the sudden obsolescence of my graphic card rigs because a new proof-of-work algorithm could be designed to appeal to the large number of graphic-card miners. It is the population of miners that provide the initial enthusiasm for a coin.