I agree, there must be a negative carry on holding RAM to discourage hoarding. Looks like the automated gradual increase of RAM supply that Daniel Larimer proposes can serve as such a “usage fee”. However, it seems weird that block producers would add more RAM automatically, without corresponding increase in market demand. Thus increasing the cost of running a full node only to fight speculators, without any benefit to real users (i.e. there will be more RAM than is needed for real apps). Wouldn’t it be better if RAM had an interest rate that accrues to block producers based on each KB of RAM?
That way users will be incentivized to release unused RAM as soon as possible. While block producers will be incentivized to add more RAM to earn more “usage fee” only when they know that this new RAM will be bought by users (i.e. there’s demand for it).
Example: you buy RAM at the market price of say 0.1EOS and when you sell it you get the new market price minus daily usage fee (say 0.00001 EOS per day). The fee is fixed in EOS and can be decided by a vote.