Any attempt at monetization through the "normal" means, such as increasing the number of ads or selling user data, would completely undermine the things that make Reddit such a valuable site. We've already seen a few examples of Reddit moving toward a more legitimate, financially viable social media model, and each one of those moves has been met with significant backlash. It seems that they're in a lose-lose situation: either run out of money to keep the site running, or lose all their users.