There is a third issue, which we saw in spades on the Phase II software: once someone is logged in, we will no longer see that person's IP and therefore will have no way to block that person--and there will most certainly be people who log in solely to upload files that should not be uploaded, and who will deserve to be blocked.
The new software is capable of blocking by IP or by login name. There just aren't yet any features in the software to add to the block list by name, or to discover the IP of a logged in user. Those will need to be added at some point; I'll add that to the tracker at high priority.