HTC is doing its best, unlike Motorola, to keep the promise Peter Chou made with regards to unlocking bootloaders. Several different phone models are now unlockable via the HTCdev website, among which all devices released after September 2011, and even prior to that date.
According to a recent tweet, new phones have been added to the unlock list. If you have an HTC Wildfire S, Wildfire, Salsa, Merge, or Desire, you can now unlock its bootloader — given that you understand the risks and that it will void your warranty. However, that never stopped the community so if you feel like, jump over to HTCdev and get the bits which will set your bootloader free.