How much are Facebook fans worth to small businesses?

One of the questions that I often get from small business owners is, "how much is a Facebook fan actually worth to my business." My answer is almost always the same. "Zero, unless..." Depending on what methodology you believe, a Facebook fan could be worth upwards of $100 or as little as $1.00. Some have speculated that fans are worth $10, based on brands advertising on Facebook and the number of impressions they get with actions taken.