I can understand artists wanting to protect their intellectual property.
On the other hand, I can play almost anything just by listening to it, so, although tab helps a little, banning unofficial tab sites is not going to slow me down much, if at all.
So yes, its silly.
I'm sure it won't be long before artists start releasing empty CDs cos their lawyers advised them to not let the public hear their songs (this would be a good thing in some cases).