Not true. My traffic comes from PPC, direct media buys, affiliates, and offline media purchases.
I control each and every traffic source. I can turn them on and off at will.
The only time I concentrate on SEO is for a term that I know converts well over time. To do otherwise is a waste of time, period.
There's plenty you can do: don't depend on them. Simple as that.
This man speaks the truth.