John Scalzi has some good things to say about I, Robot and the nature of Hollywood adaptations:
Allow me to put on my pontificating hat here and tell you an obvious truth: Hollywood doesn’t care about source material. When a major movie studio buys a novel (or in this case, a collection of stories) to adapt into a film, it stops being material of a fixed nature; it becomes suddenly fluid, and you’ll find vast chunks of the book sliding out, getting rearranged or simply being ignored for the expediencies of the filmmakers and the studio. Let me make it even more clear: It is a rare book that makes it through the film adaptation process without great violence being done to it.
And this is not always a bad thing. I think some of the most successful literary-to-film transfers have been ones in which Hollywood does what Hollywood does — substantially guts and reworks the source material to adapt it to the needs of the filmmakers. The obvious example here is Blade Runner, which is of course a mightily reworked version of Do Androids Dream of Electric Sheep? by Philip K Dick. It’s entirely possible a filmed version that is more faithful to the original novel could have been made; on the other hand, Blade Runner is excellent. It’s a fair trade.