There is no reason to buy most bootlegs. Many groups have old concerts (and some new) freely traded on such sites as the archive.org site linked by tvyankee above. For example, I have gotten a couple of Jeff Beck concerts this way. With a high speed connection, and using bit torrent (BT) you would be astonished at what is out there for free.
Another great site for downloading concerts is Easytree:
http://www.easytree.org/Note that Easytree requires registration (it's free) and that it is most likely going to cap its maximum number of registered users at 100,000. It's rapidly approaching this level now, so if you are interested at all, sign up.
There are also literally hundreds of other BT sites out there. There are also sites that promote regular mail trades for the bandwidth challenged or for those groups that don't favor electronic trading of their concerts (the Allman Brothers, for example). Post here or PM me if you have any questions or want any more links.
