The beauty of this is that it's a way for them to let people try Ubuntu Server quickly and easily. While I don't remember the articles, we've all seen the ones talking about how demand isn't linear. Lots of people will try something free that won't try something that costs even a cent. So, Canonical will pick up the 2 cent tab (the cost of one hour of a Micro instance). Many will try it. Heck, if a million people try it, it will cost Canonical $20,000. That's a lot of exposure for a small amount of money. Companies are paying way more than 2 cents per click in advertising. Booting up an instance to try it out is a lot more engagement and investment in the process than an ad click.

Canonical is getting smart people to engage with their product for several minutes (if not the whole hour) for a mere 2 cents. That's one of the best campaigns I've seen and far more effective and cheaper than AdWords for what they're doing.