8. Only Going With 8 Best Pictures
Considering how many people are currently probably compiling or reading lists of gripes like this, and wondering why their "nailed-on bet" for Best Picture didn't even make the shortlist, it seems like something of an oversight for the Academy to have gone with just the Big 8 this year. To be fair, they could have just gone with a single nomination: that's how nailed on Boyhood - the most Oscar-friendly of Oscar-friendly films - is to win, but that only highlights the fact that they could clawed in some credibility by putting in another couple of films (especially considering that two were very noticeably snubbed in one way or another).
Why It Went Wrong... The Academy probably don't want to be seen to be giving out nominations willy-nilly (especially when their lengthier lists have been accused of that in the past), so limiting makes it look like the decision was more difficult.