OnLive, the online game streaming company, is quietly introducing this weekend an interesting way to share a high-quality online game. All you have to do is share a web page link.

The new sharing system could be a big deal for game publishers as they seek to use social media to share new games. You could share the game Mafiia II, for instance, by sharing the link to it on the OnLive system via email, a tweet, or by embedding it into a web page.

OnLive is using the new sharing links to promote games that it usually merchandises on Fridays for $5 sale prices. If the user is a member of OnLive, they just click on the Play Now link in the email or web page, and the demo for Mafia II (today’s featured game) immediately starts playing. It actually skips the sign-in process for launching OnLive’s page. You just immediately start playing the game, said Steve Perlman, chief executive of Palo Alto, Calif.-based OnLive.

If they like the game, they can click to buy it for $5. That’s a very viral, friction-free way to promote a game, since it’s pretty painless and instantaneous.

If you’re not a member of OnLive, you first go to a page where you see an age gate, since Mafia II is a mature-rated game. The OnLive plug-in loads in about ten seconds. Then you can click on links to games that will launch instantly. Perlman says these promotions will now start showing up all over the place. With non-M-rated games, no age gate is necessary. You can essentially go into a full OnLive experience from any social medial or email promotion.

Gaikai, a rival game streaming service, has talked about making a similar kind of sharing system, where game publishers can promote games by embedding links to them on any site.

Here’s the first available short link, to play Mafia II now.