I just think that there is no problem at all with the "Live Earth" tour. Does it create some carbon emissions? Yes, but so does breathing. That doesn't mean that I condone useless or unimportant GHG emissions (breathing isn't without import), but the "Live Earth" tour is not useless OR unimportant. It is quite the opposite indeed!
I guess I think it's okay because what the entire show is about world-wide is the furthering and spreading forth of global warming education to the masses. A concert medium is an appropiate and effective way to appeal to a younger audience, which is the demographic we really need to educate if you think about it. All should be educated wherever possible, of course, but many of the decision makers that will make some of the most important decisions regarding our planet are attending classes right now, even as we speak...or type for that matter.
So go ahead and buy a ticket if you live near one of the tour venues. Enjoy some good music, good times, and good education that will most likely move you to action. Live Earth Rocks!!!
picture source: http://www.liveearth.org/event.php#press