The problem I see is that you have a lot of new SaaS startups where their is not a low marginal cost to add people. This is particularly true in the developer space where there are any number of startups that will record events from websites and mobile apps for anything from performance monitoring to analytics. Each free customer they add has a cost in terms of data, infrastructure and building code to scale massively. Thus, they are forced to raise ever bigger amounts of money from VCs to keep going. Contrast this with 37signals - where adding another free client really did have very little cost.

And at the same time, all these services are, as the article points out, becoming commodified. Thus, recognizing that they really can't make money in the SMB market with such low switching costs, they decide to move to the enterprise market and thus the whole economics of SaaS are blown up, and they look very much like a traditional enterprise software business - and SaaS becomes a delivery methodology rather than business model.

My own article on this issue (shameless plug): https://medium.com/i-m-h-o/a2cc0d5ba431