I'm not an expert on StorJ, but I'm the Permacoin author. As far as I can tell, Permacoin is a possible candidate for the "proof of resource" puzzle that StorJ

I'm not an expert on StorJ, but I'm the Permacoin author. As far as I can tell, Permacoin is a possible candidate for the "proof of resource" puzzle that StorJ opaquely says they'll need (though they don't provide any details). Permacoin is fairly conservative, in that we give a specific description of a storage-based puzzle, and argue that it satisfies exactly the same requirements that Bitcoin's current proof-of-work puzzle does. In other words we aimed for security first, useful side effect second (which is why we only claim to support archival storage, as opposed to full featured Dropbox-like functionality). If StorJ uses a different puzzle construction, and are not rigorous about its security, then there are two possible mistakes to make: 1. it does not correct incentivize the incentivized storage behavior - it may be possible to game their system and avoid storing useful data 2. it does not satisfy important security requirements from Bitcoin - it may be possible to game their system and make off with a lot of storjcoins using less work