Second Life competitor Meez has become a magnet for advertisers trying to reach teens and young adults. The online service is one of the top four American sites in terms of the number of minutes per month per unique visitor spent there, says comScore. That puts it ahead of Facebook and YouTube.

Hot Pockets, the microwaveable frozen snack brand, recently concluded a campaign on Meez, run by ad network AdNectar, which specializes in branded virtual goods. (We covered AdNectar’s growth last year.)

AdNectar stocked Meez with a range of Hot Pockets-branded goods. Players could buy pretend Hot Pockets, of course, but also Hot Pockets t-shirts, or even stoner-like “pizza eyes” for their Meez avatars. The young man in the screenshot has stocked up on all of the above.

There was a catch: The virtual goods were only available for two weeks. If you didn’t jump on the chance to buy the shirt, you could only seethe in envy.

“The scarcity of these items and fact you can’t get them anymore actually make them even more of a cool item to our users,” a Meez spokeswoman told me. The move resulted in far more Hot Pockets merchandise on Meez than they had forecast.

The potentially infinite, unlimited availability of digital goods has the downside of devaluing them to humans hardwired to compete for scarce resources. By making digital goods artificially scarce, marketers can raise their perceived value, whether that’s in dollars or in perceived coolness.

In fact, the Red Cross is conducting a blood drive campaign in Meez that runs out at the end of this month. The goal is to get Meez players to virtually donate blood, in hopes they’ll also do the real thing. If you want the cool donation buttons, or a replicant Nurse Lucy Meez, you need to act now. The idea is the same as Hot Pockets: Make giving blood something you feel compelled to do now rather than in some open-ended near future.