I am concerned that with the advent of many domain specific sites (webmasters, user interface, etc, etc) that StackOverflow will decrease in quality. By splitting things up this way we are decentralizing the brain-power over multiple sites. What will then happen is that someone that could easily answer my C++ question will start spending more time on the UI site and I will not get his exceptional answer simply because his attention was somewhere else.
For myself I would tend to still ask my domain specific question on SO simply because I (maybe falsely) believe SO is where most of the brainpower is still centralized and therefore I will still get a better answer.
To repeat myself, my concern is that with all the specialized sites that we will lose quality. The reason for this will be that smart people are will tend to frequent one site or another more regularly.
Am I wrong?