The author makes a valid point. What Excel was for B2B functions (e.g. accounting), Facebook is for B2C functions. So why bother? /s
Any startup should include Facebook in its competitive analysis. How are people using it? Does it work? What’s missing? And be open to the idea that a Facebook group that does even 80% of what people want might easily be your toughest competitor. You can guarantee that Facebook has already signed up 99% of your potential userbase.