100 million: the number of users on Facebook on August 26, 2008.
To put that in perspective, imagine if ALL of the residents of Mumbai, Karachi, Istanbul, Delhi, São Paulo, Moscow, Seoul, Shanghai, and Mexico City (the nine largest cities in the world), Athens GA, and Newell PA (pop. 551) were all registered Facebook users. To look at it another way, that's one-third of the US population. Either way, it's a lot of people.


Does this matter? MySpace hit 100 million users two years ago. The last time I heard someone mention MySpace was at a concert a few weeks back; the lead singer said that I could find them on MySpace. (I'd give you the link because they were pretty good - but I forgot to friend them. Oops.) MySpace may have been the first to 100 million, but remember that pioneers often end up with arrows in their back.
This user base doesn't matter enough for marketers to start formulating a "Facebook strategy." Facebook is one of many channels to choose from and may look attractive versus other social networks, but what about versus search, a loyalty program, or shopper marketing? Your job is to stay elevated above the channels; when including any social technology in your marketing, make sure you have a better reason than drive-thru marketing.
Here's why the number might matter to you. The user base has value according to Metcalfe's law. (In a nutshell, one fax machine is useless, two means we're in business.) If you are an individual and no one you know is signed up, there could be a googol of registered users and it wouldn't matter to you. If you are a marketer, the key is the overlap between 100 million users and your target audience. No overlap means no reason to care.
Odds are that as 100 million grows into 200, you will have more friends, prospects, and customers on Facebook. Then you'll have to wrestle with new issues like the ego trap.
But for now - given that Facebook has hit the 100 million mark - are you paying more attention to the site for personal and/or professional reasons?