I suspect this logic can also apply to tor exit nodes, which is more troublesome.
If you would like to read more: http://tornull.org https://trac.torproject.org/projects/tor/wiki/doc/ReducedExi...
With a minimal amount of work and upkeep. You can cut down on abuse fairly easily.
'in order to ensure that deterrent effect, it is necessary to require users to reveal their identity to be prevented from acting anonymously'
For reference: https://blog.torproject.org/running-exit-node