Quote - What I was referring to was the hardware aspect. In a CRT, increasing the voltage to the electron gun does not result in a linear increase in luminance. So a channel value of 128 ( for 8bit channels ) does not display as half-brightness, but rather as something slightly dimmer. Because of the natural physics of the electronics, the CRT is acting as a 'gamma decoder', as pointed out in the Wiki page. In order for the image to display the proper luminance values, the linear image needs to be 'gamma encoded'. An LCD does not naturally exhibit this behavior, so the electronics emulate it. On many LCDs, the gamma decoding value can be set.

As for colorspaces, here's a page that has a nice explanation of the relationship with sRGB and gamma.

actually, i find that page obscures a lot of important points and confuses others.  i find the Wikipedia page much clearer and bettter for actually implementing sRGB transformations.