GMail did set a trent, only if you got an invite you could get one...
Google does use a similar way to promote a new product GOOGLE GULP!
How to get Gulped?
You can pick up your own supply of this "limited release" product simply by turning in a used Gulp Cap at your local grocery store. How to get a Gulp Cap? Well, if you know someone who's already been "gulped," they can give you one. And if you don't know anyone who can give you one, don't worry – that just means you aren't cool. But very, very (very!) soon, you will be.
Quench your thirst for knowledge.
At Google our mission is to organize the world's information and make it useful and accessible to our users. But any piece of information's usefulness derives, to a depressing degree, from the cognitive ability of the user who's using it. That's why we're pleased to announce Google Gulp (BETA)™ with Auto-Drink™ (LIMITED RELEASE), a line of "smart drinks" designed to maximize your surfing efficiency by making you more intelligent, and less thirsty.
Think fruity. Think refreshing.
Think a DNA scanner embedded in the lip of your bottle reading all 3 gigabytes of your base pair genetic data in a fraction of a second, fine-tuning your individual hormonal cocktail in real time using our patented Auto-Drink™ technology, and slamming a truckload of electrolytic neurotransmitter smart-drug stimulants past the blood-brain barrier to achieve maximum optimization of your soon-to-be-grateful cerebral cortex. Plus, it's low in carbs! And with flavors ranging from Beta Carroty to Glutamate Grape, you'll never run out of ways to quench your thirst for knowledge.
Google Gulp! pages