The problem is that there are no very many big sites that use perl either. I knew that Amazon used Perl, than tried to use Java, than... I don't know what they use now. Google uses Python, Yahoo uses PHP, Microsoft probably uses DotNet and Sun probably uses Java.
I will add:
* LiveJournal * TypePad * Vox * Popular MT sites like: - Huffington Post - Gothamist - Talking Points Memo - many, many, many more of course
