Essentially all the article states is that a profitable business needs to have profits per user that scale according the cost per user acquisition. Viral is cheap acquisition, so profits can be less. Non-viral costs more per user and typically has a smaller market, so profits per user need to scale accordingly.
To put the article another way, there are two ways to make big money:
* Make lots of money per user
* Have lots of users and have low expenses.
No-man's land is having a £1 app that you will never realistically get more than 5,000 users on.
Good rule of thumb-- anyone who advertises heavily to consumers has a high ARPU.