Sometimes when something is expensive or hard to obtain, purchasers organize themselves into a buyers club. Their combined purchasing power enables them to negotiate a better deal, or even elicit products that might otherwise not be available.
In healthcare, for example, Group Purchasing Organizations (GPOs) enable a lot of market leverage from healthcare providers on suppliers of drugs, devices, and supplies. Not high profile, but they are gaining significant influence over the market.
In the modern political order, people who find outrage hard to create on their own, or who, for one reason or another, like their neighbors and find life disconcertingly good, can cheaply and reliably acquire outrage by joining a buyers club. This outrage is generated from a number of sources, packaged, and conveniently conveyed to the consumer.
In fact, this outrage economy is so effective, I can't even figure out how people find the time to consume as much outrage as is being created. I doubt there is any kind of bubble here--outrage is more a service than a product, consumed as it is produced, so there can be no stale inventory of outrage that someone can dump at an opportune moment, causing a crash.
Still, I wonder whether the oversupply is having something of the same effect as the oversupply of sugar and fat. As people are getting obese, they are also wearing out their adrenals by pumping out all that adrenaline and cortisol. In fact, as I write this, I realize that I might have stumbled on yet another possible explanation for the obesity epidemic. Don't blame Big Food. Blame Big Outrage.
So, we've organized ourselves to make outrage cheaper, more effective, and more refined, with less cognitive fiber. Raging more, but enjoying it less? Consider switching back to traditional outrages (neighbors, barking dogs, annoying kids) or perhaps artisanal sources (molybdenum thieves, the threat of anarcho-syndicalism). More time consuming or more expensive, but it might be healthier in the long run.
It's not like you should be worried that we'll run out of it.