Since iPhone is a computer in miniature, malware authors and anti-malware experts are already wondering on its impact on the security side of computing.
Kasperky (Web, blog entry) believes that the iPhone will be a target of malware activity, and that its operating system, OS X, will carry vulnerabilities much like its big sister.
McAfee (Web, blog entry) thinks that 2007/2008 will be a new era of malware for mobile malware, characterized by fully-functional malware, since the iPhone (and the mentioned Nokia N800) almost have the same capabilities (though in a limited way) as that of a Mac (or Linux box for N800).
The biggest implication – for me, at least – is that anti-malware and computer security companies will have to develop a solution for such platforms. This phone will be targeted by malware authors, specially if it becomes successful (as lots of people thinks it will).
Off-topic: here’s a hands-on description on the iPhone. Read the comments.