There's also the possibility they're using that Android-app-that-shall-not-be-named. If that's the case, they're not caching for free, they're freeloading. There's a big difference. The former is an approved method, while the latter is unapproved, unethical, and, in the case of this app, hurts everyone else by using unnecessary bandwidth.
If you're using the app I'm referring to, sorry, you're one of those people who's abusing the game. You may not even realize it, because the app's creators aren't very forthcoming with the impact of their app, but you are abusing the game (or at least the website).
Wow! I'm a freeloader. And I "abuse" the game.