If you intend to watch Toy Story 3 with fresh eyes and don't want to know the plotlines or plot twists, move to another thread.
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You have been warned.
http://www.ugo.com/movies/toy-story-3-interpretations
Basically what is said in this article is that the toys in the movie find out what it is like to no longer be protected and placed in an environment where you are "played with until death." while the other well established toys are left to guard you from escaping while they are given better living conditions. While the broken toys are stripped of any remaining valuables and then incinerated.
You could also make a Marxist and Stalinist comparison to... oh wait, they did that too in the article.