What I take from the article and from your comments is that Freemium is a great idea for any product that relies on network effects, either to create a more useful product or to provide a strong exit. But with any other type of product, it would make sense to put the Freemium aside. It's probably easier to try paid only (with or without trials) first, rather than starting with Freemium and dealing with the fallout of cutting off free users later on.