This post has a good explanation of long-term design issues in Ingress, similar to the ones that sunk Shadowbane.
In board game circles it’s referred to as the “runaway leader” effect – winning makes it easier and easier to keep winning. It has a few advantages – it is a more intrinsically realistic dynamic. There are some games, like Monopoly, in which a runaway leader taking over is the entire point of the game in the first place. However, runaway leader positive feedback loops are not viewed as good design for longer games because players tend to dislike games where the outcome is decided very early on but they are obliged to keep playing. While nobody is actually obliged to play Ingress, player attrition rarely helps with the underlying balance issues. Note that a game having a runaway leader effect doesn’t mean that a team in a weaker position cannot ever achieve victories – it just means that the odds are heavily stacked against them.
Like Shadowbane, Ingress is not asymmetric, so the rules are not tilted against either side, but the mechanics do make it easier for the winners to keep winning, which tends to have the effect of driving out the losing team and reducing the influx of new players (on either side, because winning unopposed on an empty field in a virtual world gets boring quickly).
I am debating whether I am interested in continuing to play. I live and work in one of those heavily dominated areas, so if I want a competitive environment, I need to drive an hour away. And people who have farmed in the non-competitive environments do that same drive with their farmed gear.
The rumored third faction only makes the runaway leader effect worse unless there is reason to unite against the winning team. MU in Ingress is like PPT in Guild Wars 2: territorial control is all that matters for the scoreboard.
While the rules of Ingress are balanced, the flavor text spurs the current imbalance towards the Resistance. Oddly, the linked post has a commenter who says this is a good thing because it keeps the game competitive. I’m not sure that person understands what “competitive” means.