If you got a few minutes and can access The Journal of Cell Biology. Read the article about impact factors. Its pretty interesting and IMPACTS you the scientist.
It is specially worth reading for those whose job performance is rated based on the impact factors of the journals in which they publish. This just shows that any system of evaluation has its problems and those doing the evaluation should maintain a human element in the equation that can look at the big picture.
I believe its very telling that Thomas Scientific will not release its actual data. A job committee should do more research on a candidates scientific work and not rely on "impact factors." In fact, based on this paper, its unethical for them to do so.
Here is another website that lists current and past impact factors for almost all journals.