Collective Action Problem
A collective action problem is a game theory problem akin to the prisoner's dilemma, but with a large number of agents, where an impasse emanates from the coordination costs associated with getting all agents to change their behavior. In essence, a collective action problem is a coordination problem.
One example is the Free Rider problem. Another well-known example is Tragedy of the Commons: a resource collectively owned will be exploited until it runs out because there is no moderating body to force restraint. Overfishing is considered to arise from tragedy of the commons. Because no one fisherman can cause overfishing, all fishermen ignore overfishing, until their actions in aggregate cause it to occur.
Trees: Trees grow tall to compete for sunlight. Trees could expend less energy if they did not grow so tall, but they must grow tall because other trees do.
Malthusian Trap: the population grows to exploit the available resources until such point as the amount of resources can no longer sustain the population. It would be optimal for the whole population to reduce its growth, but each individual in the population has the biological incentive to do the opposite. It has been theorized that the advent of agriculture created such a trap; populations expanded with the excess food until the affects of agriculture became a detriment.
Competition in industries: It would help the firms in a competitive industry to collude to rise prices, but one firm that fails to cooperate can undercut the others.
Arms races: Demilitarization is difficult because each country wants to have enough arms to protect against the next-strongest army.
Cancer: As discussed with respect to longevity, cancer is a problem of cells prioritizing their own short-term reproductive fitness over that of the organism.
The "Race-to-the-Bottom": states lower their taxes, even if they don't want to, because they have to compete with other states for firms that can easily move shop.
Higher education: Universities are overpriced, unless you consider that their values comes from their capacity as a signaling tool. It is difficult for a given student to forego their use as a signaling tool, because doing so would cause that student to fall behind their peers in the job market. Moreover, it is also difficult (but less so) for employers to ignore education credentials, because they are the status-quo signaling tools.
Others: other examples that are offered are scientific research techniques, government corruption, and the makeup of congress.