Or, for that matter, how many people are cancelling their SWTOR subscriptions ( which may seem weird, considering they're not directly related ) and swearing not to buy future DLC.
Even if said "temper trantrum" ( again, being condescending doesn't help ) is justified? I can hardly think of a better reason.
On the SWTOR front, it's actually kinda twofold. The first reason is that ME3 shares(d) the some of the same writers. And the second, which leads from the first is, if ME3 can have a lousy ending, what's to stop them from butchering SWTOR in a similar manner. That's the rational explanation, the REAL reason?
Word of mouth is still pretty powerful. Hell, it's never been not powerful. People are more willing to listen to their friends, even though they could be wrong, than actual facts. So if one person says it's bad, then people LISTEN. Even if that one person is talking out of their ass.
For the record, both Bethesda AND Valve have changed endings in their games due to fan outcry. Bethesda changed the ending in Fallout 3.
In the original, if you had only two choices. Sacrifice yourself to the Radiation or send the girl in to do it. Despite having a giant Supermutant nearby who was immune to it. The second change had you waking up after the radiation burst to keep playing, no matter which you chose.
And Valve changed Portal's ending to fit that they were making a Portal 2. As originally, there wasn't going to be. But the fans demanded a second Portal. And we got one, and it turns out it was a good thing too. Cuz P2 is AWESOME.
And apparently, the outcry is turning to charity to help get their point across: http://pc.gamespy.com/pc/mass-effect-3/1220719p1.html