The main reason speculation can be harmful in this particular case is that unlike many other tokens - RAM is “backed” by a scarce resource (memory) which cannot be practically rented. An analogy would be a real estate market in which property rentals are not possible.

There is a way to rent RAM. Or to be exact, it's owning+renting combined.

Users will buy and sell RAM like they do now. But if they have more than certain amount (that's needed for basic account), they will need to pay rent for the RAM.

Obvious problem is: What happens when the account doesn't have any tokens for paying the rent? RAM can't be taken away because it can store important information.

Solution: Accounts can go in debt. When the account receives tokens next time, the debt is automatically paid.

This is not perfect solution. There could be accounts that never pay their debt. But owning that kind of account is pretty stupid because you can't do any business with it. If people try to avoid paying rent by using other tokens than EOS core token (which would be used to automatically pay the debt), we can freeze the account when it has too much debt. The rent debt must be paid before the account can do any transactions again.

This would create quite good incentives to minimize the usage of RAM.