I'm listening to the podcast now, so I'm commenting as I go. I was massively (see what I did there?)disappointed with the ending. I've commented about, sure, but I agree that some of the outcry is pretty out there. However, the sheer scale of the rage does serve a purpose. It forces Bioware to take notice. And if the fans are upset, you lose business.
The outrage is, in fact, a unique occurrence, but its also a unique situation. Mass Effect is an interactive experience in which you guide a story of your own making. And as such there is much more emotional investment, especially after 100 hours of play. You just don't get that with movies or books. (Though I can imagine something similar happening if this happened with Harry Potter).
Having said this, I do believe the ending should be change / expanded upon. Not from an artistic standpoint, but from a business standpoint. The ending has alienated the base, and that's losing money. Regardless of whether you think it's art, it's a product for a large market and should be treated as such.
(As I progress through the podcast, I see some of these points are being made.)