On the flip side, I have been frustrated particularly at linux.conf.au last year at how "not deep" many of the talks were. Having done quite a few talks over many years at similar conferences, it's actually quite hard to nail something technical and be entertaining for a presentation at the same time. Someone who nails that quite consistently is Aaron Paterson (from the Ruby/Rails world). Watch some of his talks on Youtube.. I aspire to produce more content on a level similar to his. To combine good entertaining presentation with actually educating an audience about the technical non-obvious details of something they probably didn't know -- and something that was relevant in a practical project he took on. Working on it, not there yet...
Cut them some slack.