How Pocket Hit 20M Users with 20 People

I've only just started using the Pocket app on my Android phone, but I feel like the thing it gets right is local caching. The pages I've bookmarked are rendered perfectly even with no network access. This is actually super great, not always common, and is usually my biggest gripe with other applications (looking at you Bloomberg) as a subway commuter.

I recently abandoned Pocket because of their new recommendation engine that's selling out my personal data with the service.