Uncapped rent will lead to people getting priced out of their homes by the first person willing to outbid them. Nothing unforeseen about that.

There are others, though. For example, there are a couple of basic asymmetries that advantage landlords.

One is that they generally have multiple units, whereas renters generally have only one. So the end of a lease is a bigger deal to the renter than the landlord. Another is that the costs (in time and money) of a tenant move are much higher for the renter than the landlord.

This means that a greedy landlord can jack the rent well above market price because renters are eager to avoid the expense and disruption of moving.

> jack the rent well above market price

if the renter is able to accept the "jacked up" price, then by definition that's the market price (for that property). The renter needs to move if they don't like the price. The landlord also don't like vacant properties, and is perhaps eager to not "jack up" the price if they find that the tenant moves as soon as they do!

It is not the market price, because the only person who will pay it is the one who's eager to avoid moving. Everybody else will pay a lower price, because they have already committed to moving.

The second order effects to whats happens to those people, and to the neighborhoods where they lived is the unforeseen part.