We designed Permacoin with the goal of being rigorously secure. Our design addressed a bunch of problems that aren't (yet) addressed by filecoin. - Erasure cod

We designed Permacoin with the goal of being rigorously secure. Our design addressed a bunch of problems that aren't (yet) addressed by filecoin. - Erasure coding (over the whole dataset) guarantees that you can't just drop some of the filed and make them unrecoverable. - Preprocessing the entire dataset to be full entropy guarantees that it isn't cheaper to store one portion of the dataset than another (for example a segment with just all zeroes). - Outsource resistance: it would be a shame if someone just runs a cloud service to store the file, which would be more efficient than using local hard drives. Arguably this is already happening with Bitcoin cloud mining. Permacoin and the follow up work on nonoutsourceable puzzles address this. Without these features, the concern is that selfish miners might find ways to earn more filecoins without actually providing the useful service. Incentives are correctly aligned only when there's no way to game or cheat the system. Filecoin provides a richer interface (get and put for individual files) than Permacoin (which only guarantees recovery of the whole dataset at once). We would have supported this interface if we could figure out how to, while maintaining the same standard security properties! This is difficult (but hopefully possible) future work. On the other hand: - Maybe it will be a long time before practical ways to game filecoin catch on. - if filecoin builds a community that values altruistic participation like Tor (and even Bitcoin to some degree) it will be useful anyway - it could be possible to improve filecoin with features from Permacoin - there's a lot to learn from the actual launch of a system like this with real users