Ending (spoilers)

That shock value works with some films, but not Disney: The emotional catharsis at the end has to be there, otherwise the film would seem incomplete.

It's very important that an ending fits in with the story and mood of the film up until that point. If at the end of a fun film with lovable characters on crazy adventures, you suddenly kill off the main character at the very end for no good reason, it can leave the audience feeling shocked, betrayed and unsatisfied. But if the death is meaningful and has a higher purpose to the plot then it might work.

Example:
The end of On Her Majesty's Secret Service - Bond has just got married and has seemingly left his life as a spy to live in peace with his new wife Tracy. Then Tracy is shot by Blofeld. Bond is upset but this means he is now free to return to his old life as 007 and he now has vengeance on his mind, thereby setting up the next film in the series (although Diamonds are Forever was a letdown on that front). So Tracy's death right at the end has purpose and meaning, and it fits in with the nature of the World that Bond lives in: people that are close to him tend to die, it's a hard truth.

So I'm glad Wall-E got his memory back and finally has that romantic moment with Eve. The film was building up to that, it would have been harsh to deny that moment to the audience.

I love this movie, but the ending was definitely lame. The chip that was fried was some sort of RAM chip. He wouldn't lose any memories. Even if he did, a shock would not bring them back. It was just a last ditch effort to pull at the heart strings of the audience. That was easily the weakest part of the film, but it was otherwise pretty great in my opinion.