The advantage of starting with consumer motivations, as opposed to trying to figure out what social media application to use, is that it makes clear how seemingly disparate applications are actually quite similar if they share the same underlying motivations for use. This makes the job of creating integrated marketing campaigns not only less overwhelming for the manager but also much more closely tied to online consumer behavior.
In other words, the question is not whether to blog or tweet, but what objectives need to be achieved and which set of tools with their corresponding metrics can best achieve them.