Bitcoin is vulnerable to a DOS or DDOS attack if a user decides to commit multiple transactions instead of one.
It can potentially cause an overload on the miners.
In some cases it is enforced upon users, for example when they purchase a large amount and have to buy from multiple sources.
The rising fees seem like a partial defense against this, but I recently read that the miners agreed to lower the fee to about 0.15$ if I remember correctly.
The cycle which leads to an irreversible rise in hashing difficulty over time and a rise in fees, while constituting a partial defense against DOS and DDOS, is a vulnerability to the profitability of mining and hashing and by this, to the profitability of transacting over the proof of work blockchain.
Some of my previous blog posts were about this issue.
2*. It also means high dependency on energy prices and carbon tax, which now I see another reason to why the ruling class may want to enforce.
- The size of the blockchain itself is monotonically growing and by this makes the storing of the blockchain more expensive, queries slower and thus, more expensive, and the installation of a contributing wallet (which has its own copy of the blockchain) slower and more expensive.