If you use a PRNG to seed an incremental counter on every node, and you get one collision, you are bound to get zillions of them.<p>On the plus side, I think that means the risk that you get a collision is smaller.<p>Also, using bare incrementing counters may be a bad idea for different reasons: it allows attackers to guess IDs of future messages. You can counteract that by hashing the IDs using a good cryptographic hash function, but that effectively turns your ID generating process into a PRNG.