Additional thought: I would love to see an implementation of time-locked secrets for GPUs. They are such massively parallel architectures that this would allow the informant to spend very little time computing the chains, while requiring a lot of time for the public to unlock it.

For concrete numbers: I wrote a Bitcoin miner for AMD GPUs (which was at some point the fastest available). A single ALU on the Radeon HD 6990 can do about 500k SHA256 hash/sec (~1/4 the speed of a high-end CPU core). But it has 3072 ALUs. So the informant could spend ~1 day GPU-time-locking a secret that would take ~2 years to CPU-unlock!