I love their best argument: this rock was to heavy to move so it must've been aliens!
From another board I frequent:
My favourite caption for that picture is "I didn't hear your question but the answer is Aliens."
The show, for the most part, is a steaming pile of BS. My girlfriend and I watched the first few seasons and found it moderately entertaining and a few "theories" were intriguing enough to dig a little deeper into. Then the fourth season arrived and it was simply re-hashing the same old stories from the earlier seasons and neither of us could sit through an episode without groaning and turning it off.
Some of their guests are interesting choices and there seems to be some selective editing going on. In season one or two, they had Graham Hancock and Robert Bauval and neither of them have ever expressed a belief in ancient aliens. Last year, when we interviewed Duncan Lunan (who knows both of them), he stated that Hancock doesn't believe in aliens at all and that he believes in an ancient advanced human civilisation.
South Park did a lovely job sending the show up with their History Channel Thanksgiving episode.