Lets take a look at the languages being used..

Languages Used in popular sites....

1. Google – Java (Web),C (indexing).
2. Facebook – PHP.
3. YouTube- Flash,Python, Java.
4. Yahoo– PHP and Java.
5.MicrosoftLive.com–.NET
6. Wikipedia – PHP
7. Blogger – Java
8. MSN – .NET
9.Twitter – Ruby on Rails, Scala,Java.

Hope its useful to you....