A couple of article in Stratechery about Platforms and Aggregators.  Took me a while to digest this and understand the distinction.  The two articles are:  The Bill Gates Line and The Cost of Developers (which discusses the Microsoft acquisition GitHub).  The (paraphrased) Bill Gates quote discussing Facebook maybe sums it all up:

“This isn’t a platform. A platform is when the economic value of everybody that uses it, exceeds the value of the company that creates it. Then it’s a platform.”