I suppose it's fair game to rathole on Bitcoin because OP was the first to mention it....
It would have been interesting if Bitcoin had included a rule that coins must move every 100,000 blocks or so (about two years) or else were gradually returned to the pool of unmined bitcoin. Only gradual would help increase the chance that a half-asleep holder might notice a slow drain and do something about it, and it would reduce mining windfalls from thousands of coins returning all at once in a certain block. Lost or abandoned bitcoin would eventually return to circulation, and holders would better understand from the outset that preserving their keys was an active responsibility.
I like that idea. Although, I'd imagine that most wallet software would then automatically send itself a transaction periodically to prevent it's Bitcoin from being reclaimed.
If lots of wallets did that then it would likely clog up the blockchain with lots of people sending money to themselves. But that wouldn't be a problem if Bitcoin was actually scalable.
Good point on the churn, but perhaps it's not a fatal problem. In fact, it might encourage faster adoption of more space-efficient schemes like Segwit, which is one of many ways to improve scalability.
It would have been interesting if Bitcoin had included a rule that coins must move every 100,000 blocks or so (about two years) or else were gradually returned to the pool of unmined bitcoin. Only gradual would help increase the chance that a half-asleep holder might notice a slow drain and do something about it, and it would reduce mining windfalls from thousands of coins returning all at once in a certain block. Lost or abandoned bitcoin would eventually return to circulation, and holders would better understand from the outset that preserving their keys was an active responsibility.