Currently there are many spam generate ID txn in the network and normal nodes need to wait really a long time to join or have to pay. One way to prevent such attack is by adding a (non-trivial) minimal registration fee when generating ID, but it then becomes inconvenient to people who want to start mining, and any one-click solution will be no longer one-click anymore.
What is being proposed here is another solution (that has been proposed in S/Kademlia as crypto puzzle): adding a PoW task when generating an ID. For example, we can require that the txn hash of the generating ID txn be smaller than a threshold such that it takes X minutes on average for a normal CPU to find a solution. The advantage of this solution is that it can effectively reduce attacks (given appropriate parameter) while still making it free for normal users to join, at the cost of X minutes of waiting time on average.