Music streaming service MOG has announced that it is adding a free, advertising-supported subscription plan. The move, which is almost certainly a response to the recent U.S. launch of Spotify, is designed to attract more people to the service's 11 million song library of all-you-can-stream music.

Previously, MOG was only available in one of two paid "premium" flavors. European sensation Spotify launched in the U.S. with two premium tiers as well, but crucially included a free subscription service with ads and some modest limitations on streaming. Spotify picked up 1.4 million American users in its first few weeks.

This move is certain to put some pressure on other services, such as Rdio, who offer similar on-demand music streaming but only via paid monthly subscriptions.

To sign up for a free MOG account, users need only to connect their Facebook account. Upon doing so, you'll be shown a list of recommended artists based on the music preferences found on your Facebook profile, which is actually a pretty smart way to invite users and something Spotify could have done a better job of.

The free account comes with 14 days of unlimited streaming, including on mobile devices. After that, you'll either have to pay up or live with a few limitations.

Since its founding in 2005, MOG has raised nearly $25 million in funding. In addition to its desktop-friendly Web app, the company offers mobile and TV apps for iOS, Android, Boxee and Roku.