There is currently a large discussion on /. about Yahoo moving to PHP. Well more of an argument between programmers about their favourite web coding environment.

However they appear to be forgetting the basics of engineering. When presented with a problem:
* You analyise it
* You examine the tools available for solving the problem
* You test, experiment, benchmark and generally evaluate the best fit tool(s)
* You choose your tools based on the results of the above

You don't just use PHP or J2EE because you like it or have used it the most.