I disagree - there exist SaaS companies that have successfully executed and are on the path to successfully executing the profitable B2B SaaS model. Take Constant Contact, Responsys, and Blackbaud. While not all of these companies are highly profitable, they are all proof (and will be increasingly so) that B2B SaaS companies can reach profitability. The names we all know (e.g. Salesforce, Workday, etc.) simply need more time to reach that point of profitability, but they're on their way.
Looking at Jason's example specifically, I have a couple issues:
1) Assuming a fairly strong churn rate (~20%/year), the base of customers for which CAC has been repaid will make up an increasingly large portion of the user base as the company grows (in later stages). Forgive me if I'm wrong, but it seems much of Jason's argument is based around the assumption that acquiring new customers (S&M) in conjunction with ongoing R&D and G&A will always outweigh the gross profit generated by the existing customer base. Maybe if he defines "healthy growth rate" as 50%+, then yes, sure, it will always be outweighed, but let's be reasonable.
2) If Jason is going with 30% COGS, his LTV metric is off. No startup business in its right mind would continue operating with a CAC/LTV of 2.53. We're talking double that in most cases with a bare minimum of 3.
Finally, while this is a good discussion to have, I think we're all a bit naive to think that a bunch of small-scale startup entrepreneurs have enough knowledge, experience, or expertise to questions the decisions of many large, long-standing investment firms and successful individuals that all have supported these unprofitable companies with expectations of their eventual profitability. Having worked at a late-stage investment firm, I looked very closely at 100+ of the leading, big-name SaaS companies (we're talking 1000+ pages of diligence in aggregate). From experience, I can tell you there is plenty of work, far more than just a short article and some speculation, that points to the fact that these companies will reach profitability.