Pjman - 4:29 pm on Jun 11, 2013 (gmt 0)
I must note that I only notice this on my older sites 8+ years.
My newer sites don't experience this, I have several new
(<3 years old) sites where this phenomenon doesn't hold true. The Direct Traffic vs. G referrals ratio on those three fluctuate all the time. Newsletters don't affect the ratio at all.
It's as if G is saying, "Old sites: We gave you traffic for years. If you were really that good, people would still come to you regardless of the traffic we send to you!"