According to a Fortune story, the email exchange between Jobs and an angry iPhone 4 users is fake. They said an unnamed "top Apple spokesman emphatically denied it". Apple hasn't officially made any public statements on the matter.
According to Fortune's source:
Asked on the record whether Steve Jobs was the author of any or all of these statements, a top Apple spokesman emphatically denied it.
It's worth a reminder—and we do tend to mention it often—that things routinely used to confirm the authenticity of email exchanges with the Apple CEO—such as email header information—can be faked and therefore some skepticism should be shown at times. This is, according to the Fortune story, one of those times. [CNN]