When App.net kicked off its Twitter rivalry, the $50 yearly subscription fee was based on the assumption that the ad-free social service would maintain 10,000 customers. Founder Dalton Caldwell may have underestimated year-one adoption by just a tad: he now has nearly 20,000 customers on his hands in less than two months, which throws the previous economies of scale out the window. The pain for Caldwell's business model is a pleasure for fans, however. App.net's price of entry has dropped to $36 per year, with existing memberships' durations extended to match the new yearly rate. Anyone on the fence also has a chance to try the service for a short stint through a $5 monthly plan. While it's hard to know if the price drop will sustain the early runaway pace, it reflects a determination to play for keeps in the social media game -- an important trait when the chief opponent isn't sitting still.