Wasn't the ending so bad that people actually threatened to sue?
More than that actually. it spawned a fund raising drive which had something to do with sending cupcakes to BioWare HQ as some kind FU. Makes no sense, so don't ask me. I also believe they were reported to the federal version of a Better Business Bureau or something.
Some details are hazey, due to me not wanting to remember that dark chapter of the BSN. I do remember people made an attempt to tank ME3s score on Metacritic. Even got into the news.
Bascially, the Extended Cut DLC was the response to an overwhelming outcry/attempted sabotage from the community. It really is an example of what not to do as a developer.