IMHO GPU's turned a project like Bitcoin (a decentralized currency) and turned it into a gaining investment. GPU's gave way to farming, and thus gave way to an enhanced deflationary symptom. Without GPU's, I personally don't think we'd be in the situation we are in now.
Please explain. The number of coins generated is static. Had GPU mining been impossible when prices spiked you would have seen CPU farms being built instead. Find the combination of hardware which produces the most MH/W. If 1 unit is profitable then 10 units are 10x as profitable. Also without the improved economics of GPU we all would be hashing of FPGA. FPGA destroy CPU in both price and efficiency. Adoption has only been slow because the higher cost (relative to GPU) outweighs the higher efficiency in the mind of most miners. Still the trend is inevitable.
If Bitcoin lasts long enough we will go all the way to custom ASICs.
Unoptomized CPU -> OpenCL CPU miners -> GPU miners -> FPGA miners -> SASIC miners -> Full custom ASIC miners.
Blaming GPU is like blaming the Irish immigrants for all the ills of America circa early 1800s.