If 90% of your traffic is coming from Facebook, then what would you do if Facebook’s next policy change tampers with your traffic flow?

If Google search (paid and organic) makes up 90% of your traffic, then what are you going to do if a financially backed competitor purchases your keywords and steals your traffic?

Don’t put all of your eggs in one basket, keep a diverse portfolio of incoming traffic sources. It’s much safer for the success of your website.