I refactored the previous entry so that both topics are cleanly separated.
Here's an interesting question: If a) we want people to be emotionally involved while playing games (e.g. if we want them to cry), and b) we acknowledge the effects described above, then it's kind of hard to deny games have an effect on people, a strong and intentional effect. Yes yes, so do other media, and millions of people don't go off to do stupid things. But it's useful to keep this in mind when thinking about the effects of games. Let's not pretend there are no effects whatsoever.
I think this is obvious, but I also think that the classical defense from game developers in the 'Do games make one violent?' question is, or is based on, the idea that games have no effects whatsoever, and therefore developers have no responsibility. The real question is more complicated than that.
Nathan's point about the army (in his comment in the previous entry) reminds me that the whole idea behind the army training games and arguably all 'serious' games is that they have an effect on people.