SAN FRANCISCO -- I ran into iLike CEo Ali Partovi on Monday, just after he announced a partnership with Billboard to create a new music chart based on social media.

I asked Partovi what that means. He said it will be able to measure different things than Billboard's traditional business, which focuses on ranking music played on the radio or is purchased.

He gave the example of Radiohead, the band that sold music exclusively off its Web site.

He said there was no way that work would have come up on any of the charts.

Billboard will be tracking two types of social music -- what people store on their computer and the habits of iLike users on Facebook.

Partovi said by tracking what people keep on the computer, you can see what tracks are popular. A user may buy a CD in the store, but rip only a few tracks onto his computer.

On the Facebook version, songs or music will have a longer shelf life. The top hits will more reflect favorites over the long haul, rather than what is being listened to or purchased that week.

For this reason, Partovi said the partnership was just as important for Billboard as it was iLike to get Billboard's brand associated with its services.