These are growth activities as opposed to the others you list. The truth is many products never have just organic "viral" growth. They need ads, sales, or both to drive it.
Investor confidence in interest rates being low for a long time makes investors comfortable with current public equity valuations (besides all of the other things low interest rates can do to asset prices.) It is even more interesting now because a big jump in interest rates would cripple the US budget with debt payments.
One of the things I think about a lot is what is the fair market value of certain technology companies? It would be helpful to be back at a place where I know Netflix, Facebook, etc, are worth more than their public valuations. Additionally it would be healthy for the long term human impact of tech to extinguish some of the arrogance that has been building up for the past decade.