Evan Williams wrote a really good piece on Medium this week about the value of Twitter versus the value of Instagram, and in a wider sense, the difficulty or even impossibility of measuring the value of these sites, or comparing one to another.
Williams founded Blogger, then Twitter, and now Medium. He has spent more time thinking about online content and business models than most people.
Numbers are important. Number of users is important. So are lots of other things. Different services create value in different ways. Trust your gut as much (or more) than the numbers. Figure out what matters and build something good.
Amen to that.