The main focus of this post is an issue with the game design of Ingress. Not to be confused with UI design, game design is about the rules of the game.
So, let's start with the game itself for those who have never heard about it: It is a location based game that utilizes Google Maps. Your role in the game is an agent of one of the two big factions (green and blue) who struggle with each other to control humanity. (More info) Your goal is to increase the number of humans under your faction's influence, which is basically done by establishing fields over areas and destroying the fields created by the opposing faction.
This is the theory. The practice is: You go around, try to find portals, hack them for items and AP (the local variant of XP) so that you can level up and use better stuff, and when you have a lot of good stuff, you can attack enemy portals. There are several ways to get AP: Hack or attack enemy portals, conquer grey (unowned) portals, upgrade or link friendly portals.
Portals can be conquered by installing resonators on grey ones. When you attack an enemy portal, you actually damage the installed resonators, and if you are able to destroy all of the installed resonators on a given portal, it becomes grey. Resonators also loose energy over time, and you need to recharge them to prevent them from destruction.
So, my first statement about the game is that it is fun. Not in the sense that you would spend hours with the game every night, but it's good fun, and it is something to do when you go to work, or doing some similar boring stuff in the city. Yet, I think, there is a fundamental problem with the game design.
It is quite easy to see what. There is only one question you need to ask yourself: what is the point of recharging a portal? And the answer is: Nothing.
The rules of the game are created in a way that you are interested in hacking enemy portals more than hacking friendly ones. You are also interested in attacking enemy portals, taking them down, making them your own. Because all of this will yield AP for you. What you are NOT interested in is defending your portals. Actually, you want them to be taken from you, so that you can attack them again.
When you reach the maximum level, your focus shifts. There is no point of earning AP any more, and all you need is simply more stuff. You start to play for the joy of attacking enemy portals.
In either case, what you don't want is to have a lot of portals around your frequented places which are owned by your own faction. You need enemy portals. So you stop recharging your own. You don't install portal shields any more. You don't even upgrade the conquered portals to the maximum level.
You are working for the enemy.