Sorcha, I don't think it will stop where the law is on his side and unfortuntely, whether we like it or not there are many copyright infringements.
I think the Harry Fox agency does use bullying tactics though and the way Max handled it here was excellent. Rather than being intimidated, he asked them to identify which songs they objected to and simply removed those few.
This is probably a simple soulution for something like the DT database where much of the stuff is PD and probably there are many folk song writers who have copyrighted stuff but would be pleased to see them in something like the DT but I doubt the situation with other more comercial forms of music would be the same.
JAB, TAB sounds complicated to me, I don't know but even with a PD song, given exact fingering could it be argued that they are duplcating XXX as played by YYY that maybe copyrighted?
All that said, these are just my thoughts and I don't understand copyright law. Personally, I just wish he would leave these sites alone.