I plan to get a PhD in CS, concentrating in some subfield of artificial intelligence, not sure which one at the moment. I'm looking into R&D departments in industry, but there don't seem to be too many.
For example, I have literally found hundreds of labs for the basic sciences and other engineering fields, but for CS I've found: Google, IBM Research, Microsoft Research, Yahoo Research, AT&T Research and GE Research. Are there not tons of companies like there are in other disciplines?
It depends on what you mean by R&D. Your research background will give you a breadth of knowledge and demonstrated ability to pursue problems deeply. Most open-minded companies will give you a chance to innovate to tangibly improve their products, their product offering, and increase profits. This makes sense, but the work has to be practical.
Few companies will give you a check for a year to theorize and try random off-the-wall things, even if that may lead to fantastic ideas in the end. That kind of risk is too high for most small to medium sized businesses.
The companies you listed are large and have deep pockets -- so much that it is possible for them to make long-term investments and fund more basic CS research with hopes that it leads to huge payoffs in the end. These companies have research groups that mimic the setting at universities.
You are correct in believing that such companies are rare. Pure R&D departments have a significant investment of capital and time before they get a payoff, and as such, are not viable for any but the largest and already-successful companies.
Some of the ones that do offer such a benefit, such as Google or Valve, eschew a "department" in favor of "do whatever you want time" in which you can innovate as you please during your work time (at a rate of 20% and 100% of your time, respectively). Of course, they do this only because they believe, as it has statistically proved, to be profitable for them in the long run. It all comes down to money, in the end.
