I really don't understand...lets think this through...
Lets split bands into two catagories: Those who have official tab books and those that don't
First, lets take those that do. Now, to release a tab book you've gotta be pretty fecking big to start with, so you're not exactly loosing a lot of money, or any money that you need by downloading tabs transcribed by ear which aren't necessarily accurate.
Then those that don't have tab books are generally small bands, and the only way you can get tabs for them is by sites such as MSB. And many of these bands actually support these sites and encourage downloads from them. And seeing as they don't have tab books available, they're not loosing anything, merely gaining more fans. By the time they do get tab books, they then fall into the above catagory.
This has hit me pretty hard. I'm a completely self-taught guitarist, and most of what I know has been learnt through downloading tabs through MSB, playing them, seeing how they're played etc etc. It pisses me off that a few large corperations can destroy such a valuable resource for many.