When did the UFC become mainstream?

I was watching BJ Penn vs Matt Hughes at UFC 46, this was like in 2004. And on the commentary Joe Rogan was saying how its huge for a sponsor like...

Source: http://www.mmaforum.com/ufc/89524-when-did-ufc-become-mainstream.html

Matt Andersen Alex Andrade Jermaine Andrè Yoji Anjo