I'm going to have to beg to differ on the availability of low cost web serving for people who are just trying to get into it.

EC 2 will give me a small Linux machine for 10 cents/hour. That's about $70/month and I need to be comfortable administering my own machine. If I go somewhere like http://www.westhost.com/web-hosting/index.html I can get a web host with FastCGI for $13/month. But I have to know to ask for it. (Writing a bunch of CGI then finding out that you really should rewrite it for mod_perl sucks. Yes, we know how to use Catalyst to write an application that will run either way, but beginners don't.) The same place offers me PHP for $9/month. If I go to http://www.hostmonster.com/ I can get up and running with PHP for $4/month.

For a business those costs are trivial compared to the cost of hiring an employee who can do something with that site. But to a starving student who just wants to make their own cool site, those cost differences are very significant. And I am sure that those cost differences don't hurt PHP's adoption rates one bit.