This is the root of my concern with where Facebook and Google are heading.

In the email world, you invested in building your house list, and it was likely your most valuable marketing asset.

You...

-- Controlled it

-- Could associate whatever data with it you had access to

-- You could (pending deliverability) communicate with them as frequently as you wanted for a fixed/variable rate depending on what your send costs were. For most ESPs (email service providers) there is typically a fixed platform fee, and a variable volume fee

-- Most importantly, your costs to message to your acquired audience was relatively fixed which helped balance the variable cost of acquiring them

With Facebook, they abused the trust marketers put into them. From day one the conversation was about building your brand's presence on Facebook with the "understanding" you would more or less be able to communicate with your audience freely once you invested in building the list.

I put "understanding" in quotes because there was of course nothing ever spelled out...but that was literally how it worked at the time, so it became understood to be how it worked.

The reality of what Facebook has done and where they are going has changed that relationship...

-- They want you to invest a variable (and likely ever increasing) cost to build your list within Facebook

-- They own the majority of the data on that list and their targeting tools are essentially you renting that information from them

-- They own your list, and want to charge you a variable cost via a black box algorithm to reach said list at the scale/frequency you desire

It is this last part that is the biggest issue. Email was a space where marketers had control over their ability to reach their opt-in audience, not the platform or network. But fixed-price models are not always as profitable as variable priced models run through a black box.

My broader fear is that Google has come to the same conclusion, and Inbox (and the tabs before that) is the first manifestation that Google is working on a serious monetization play for email beyond the horrid Gmail placements in AdSense and whatever targeting data they may be able to indirectly monetize.

He who owns the ability to reach that contact list has a company by the balls. End of story. Once you have that, why charge them a fixed rate when you can maximize profit by tweaking whatever variables you want whenever it suits you with regards to the costs (ie. the auction model)?

It remains to be seen if Google is going down that path, but it is clear Facebook already has. There is still hope for off-site ads with them for advertisers who know how to measure it from a conversion standpoint, and more importantly, a cross-channel attribution perspective. Social tends to be more of an awareness/upper-funnel driver when you can see the birds-eye attribution picture, with some exceptions like mobile app installs that see success from a direct response standpoint.

Smart marketers will likely focus on owning their audience data to market to them as much on their terms and a predictable cost structure as possible. Their continued ability to do so may be largely out of their control however if the companies who own the ability to reach their "list" have visions of being more than a basic fixed-price conduit.