I agree with the original post--there have been several occasions--particularly in Seattle--where I'll see a great live show (and a great live show doesn't just mean jumping around--but that's another topic) and then listen to the album-which will be not-so-hot when listened to at home-in the car--or with friends that I've instructed MUST hear this new band that might be the greatest thing since front shirt pockets. Having seen the live show--I can remember how the band performed the same songs--how the band connected with the audience--and how I connected with them performing their music. That's not to say I haven't put records on at home and been blown away.
However, if I hear a so-so album and then go to the show--it seems to be far less likely that they change my mind--it does happen--punk and harder rock bands are good examples. It's quite difficult to capture the energy of a great rock show or the transedence of an acoustic or ethereal rock performance on tape.
This is just my 2 cents though! Flame away, good posters, flame away!