Microsoft recently ran a promotion in which Farmville players received 3 Farm Cash to become Facebook fans of the Bing search engine page. Silicon Valley Insider called this a "bribe."
David Berkowitz of MediaPost notes that Bing increased its Facebook fan base from 100,000 to over 500,000 during the one-day promo. He also discusses ways to assess the success of Microsoft's promotion.
Here's my bottom line: Awareness is just the start. Why not offer Farm Cash? It's as good a way as any to increase awareness in a hurry.
Microsoft's major challenge is to change searchers' behavior, and that's a bigger issue than simply adding fans. Gaining fans doesn't necessarily translate into higher Bing usage or long-term loyalty. It will take time to know whether these fans actually try Bing and then decide to stick with it instead of whatever search engine they typically use.