The BBC reports that twenty million people wanted to purchase tickets to the historic Led Zeppelin show held at the O2 Arena on December 10, 2007. With only 20,000 tickets available, needless to say there were many disappointed fans who couldn't be there when the band took the stage for the first time in 19 years.
Your actions completely underestimate the power of a rabid fan base to help sell legal recordings, which is, after all, what you want. I am absolutely confident that the buzz generated by the concerts is selling millions of dollars of Led Zeppelin recordings.
The availability of YouTube clips enhances your sales and you shouldn't worry about these low quality fan tributes. I, for one, am replacing my vinyl recordings with Led Zeppelin CDs and I'm sure many other people are as well. All because we’ve been exposed, briefly, to the power of this band (which many of us may have ignored for several decades) via fleeting images of a concert we would have traveled halfway around the world to see if tickets had been available.
Yes, I understand the paid content world. My book publisher, Wiley, was supportive when I made parts of my book available for free on my blog and on many other blogs and in magazines. We know that it sells books (nearly 30,000 as of this writing) when people have a taste of what they will be buying. The free publicity that's generated by viral, word-of-mouse marketing can be worth millions of dollars and you’re missing a tremendous opportunity to harness that power.
I encourage you to re-think your knee-jerk legal-eagle impulse to clamp down on fans with draconian measures and consider the power that the Web has to sell your artists music.