How important is it to have keywords in a domain name?

This is an interesting video. One of my sites, the saving money site, has a keyword in the domain name related to the subject matter. The other one, my entertainment column, has a domain name that matches the column title, which sort of has to do with entertainment.

I'm researching a new site and I've been giving a lot of thought to whether I want something simple that doesn't necessarily already have a meaning or if I want something descriptive. It's nice to get something straight from Google's mouth.