Quite a while back someone mentioned that relays were about to start requiring POW to post, and I got quite concerned that I wouldn't be able to post anymore so I added the POW feature in about an hour. Here we are almost 2 months later and no relay that I'm aware of requires POW.

BTW: I divide up the space of 64-bit numbers into N sections (N=number of cores) and start one thread for each that sequentially scans through their section of possible nonces, with the nonce attempt being the next number, and when the signature has the requisite leading zeroes, it signals success so that all the threads stop.