I'll second this. It doesn't mean that these others can't exist (Foursquare is a big example), but there seems to be a valley of death for these types. Either go massively big or fail.
At least with a pay for use pricing scheme a company can do well and grow slowly without having to hit that massive knockout.
As an entrepreneur, this is why I favor starting B2B businesses. Sure, I would love to create the next Internet/social phenomenon like YouTube, but those markets are largely winner take all.
In B2B, you can be #2, #5, #10 or even higher and still have a successful business. Back in the 90s I worked with an email marketing company that scaled way too fast. The thinking was "get big or go home." Even as it cratered during the dot-com crash, small players were emerging all the time, and many of them are thriving today.
Typically in a B2C business, users don't care much to know how long you have existed or how long you will exist. If you shut shop, they switch to using another free service.
But that's not the case in B2B. I do agree that B2B is more lucrative. But, how do you convey to your potential customers that your service is here to stay. Businesses are not comfortable moving from one service to another. And, with so many start ups dying fast or pivoting fast, what's the best way for a service to build trust with its potential customers?
At least with a pay for use pricing scheme a company can do well and grow slowly without having to hit that massive knockout.