If we take them at their word that they're committed to keeping a fully-featured free version, what options do they have to make back a multiple of that $100 million for their investors? What many other companies have done in the past is to add a lot of new features. There are many examples of a simple, no-frills application turning into a bloated, complicated one, with a tiered subscription system. Ultimately a less streamlined, more expensive version of what it was before the funding.