Facebook could write their stuff in COBOL and it wouldn't matter to anyone else. Remember MySpace? It was written in ColdFusion, so I guess ColdFusion is a great idea!

Wikipedia's Mediawiki software is awful, and serves as a great example of how not to build an application. It makes WordPress look like a precision engineered Swiss watch.

Yahoo uses PHP because, like Facebook, they could make FORTRAN work in production if they wanted to.