These are much more technical and don't even mention the more obvious issues: Block settling time: If a transaction isn't complete until 1 (or n) blocks have

These are much more technical and don't even mention the more obvious issues: Block settling time: If a transaction isn't complete until 1 (or n) blocks have been committed, and mining a block takes meaningful time, then this places significant constraints on spending. If I go to the store, and buy something with bitcoin, but it takes 20 minutes for the next block to be mined, does the store need to hold the goods in escrow until the transaction clears leaving me stuck waiting for 20 minutes? There's also no guarantee that my transaction ends up in the next block being mined, so I may need to wait an indeterminate amount of time before I can walk out with my paper towels - horrible UX. Lack of physical cash: if the power is out, how do we do business? Tension between wallet security and convenience of spend.