I understand it when they go after people downloading a song, but I'm confused about the tabs. Most of these tabs aren't even real tabs, it's what someone thinks the tabs are.
Copyrights - If the tabs are online (even if it's just guesswork), it's harder to sell sheet music for the songs. Thing is I'm not sure how enforceable any of it is.
A few examples - Let's say instead of guitars it's bugle music. I come up with a really fancy bugle riff and lots of people like it. I can write out the notes on sheet music and sell it to people. If you buy my sheet music and give it away to people, it's copyright infringement and I probably can legally make you stop and sue you for what I would have sold it for. Now if you listen to a recording of my bugle riff and imitate it and think you are pretty close and give away your interpretation of it, I probably can still sue on the basis of lost wages, but it's much less clear-cut.
Similar - I set up "Tiger-Heli's Chocolate Chip Cookies" and sell them. You find my recipe and make the same cookies and sell them as "Dartful's Cookies" - I can sue since they are the same cookie. You make a slightly different cookie (less chips so you make more profit), and it's fair trade and nothing I can do - in fact I would probably be in anti-trust violation to stop you. You try my cookies and say, hmmn, tastes like Tiger used this and this and sell "Dartful's Cookies that taste almost as good as Tiger-Heli's" and the line is much less clear-cut.