CPUs were mining for approximately 2 years before GPU mining started. The first GPU miner was known to keep the mining software to himself and mined a lot of coin at the time before public GPU mining software became available. There was no great outrage about this at the time because bitcoin was only worth a few cents still until GPU mining became publicly available. After that GPU mining was generally quite available through simple GPU miners which I consolidated into the general purpose cgminer application to make it available everywhere. FPGA miners came out about  year later but were never popular because the initial cost of purchasing the FPGA miner never offset the savings in electricity they had over GPUs. They did not have significantly higher hashrate than the GPUs. When the first ASICs appeared the following year, their hashrate was so much higher than GPUs that it would have been impossible to hide their hashrate. The highest spec GPU at the time was 700MH and the first ASIC was 70GH. We all could see the sudden rise in network hashrate and difficulty followed it. We also knew who got the first ASIC miner itself and we were watching his hashrate...