When most of us think “social media marketing” we initially jump to notables like Facebook, Twitter, YouTube and MySpace. This stems to reason given their mass appeal and broad user-bases. However, deciding where to invest your time and energy depends entirely on your objectives. As demonstrated by the Hitwise data, there are a number of other communities that you may be overlooking.
A recent article with Scott Monty (who runs social media efforts for the Ford Motor Company,) identified that they (Ford) use social media essentially because a.) That’s where discussions are taking place that are relevant to them, and b.) Ford need to be a part of these conversations “in a way that humanizes the company at every turn.” To ensure they remain relevant, the Ford Motor Company uses Twitter, Facebook, Flickr, YouTube, Scribd, and Delicious (amongst other social properties), and constantly monitors new emerging platforms and user-communities to see where people are going and the latest trends online.
Have you considered sites like Tagged or Yahoo Profiles/Groups to find your influencers? Are you considering forums (and other segmented groups) that specifically pertain to your niche? Forums and focused communities can in some cases prove to be more valuable tools than much larger user-groups like Facebook or Twitter. This is because you’re extending the right message to the right person at the right time. Over and over again it's been proven - - in this new media landscape one needs to be thinking more sniper-rifle and less shotgun. ;)
NOTE: This [September 2009] Hitwise data from which MarketingCharts compiled the above graph is based on US market share of visits - -as defined by the IAB, which is the percentage of online traffic to the domain or category, from Hitwise's sample of 10 million US Internet users.