With its recent announcement to support ActiveSync on the iPhone, Apple is clearly going after the enterprise user.
The problem, as Colin puts it, is that the decisions that consumers make decisions on a radically different set of criteria than organizations. Lack of Exchange support was surely holding back enterprise adoption, so that move was both obvious and inevitable. The fact that they are also supporting remote wipe is a bigger deal than most might realize too - security is a major concern for large enterprises, and for a long time Blackberry was the de facto device in large part because of this. (Windows Mobiles devices weren't allowed at my last job until the Remote Wipe feature was enabled).
Fundamentally, I think we're moving to a model where enterprises are going to demand a certain baseline for devices to play in their garden. Features like over-the-air Exchange connectivity, remote wipe, and support for .NET, Java, and Flash are quickly becoming non-negotiable. It also makes sense given the sentiment I've seen in enterprises towards a "bring your own device" mentality. This approach makes sense for both the employees and the company - employees already don't want to carry multiple devices and can choose the ones they like, and the enterprises are spared a major expense by not having to purchase and maintain their own devices. But, to be a supported, a device needs to bring this baseline demanded by the enterprises. This is why it doesn't surprise me that Microsoft is licensing Flash Lite for Windows Mobile as well as developing Silverlight for these devices.
To understand why I think this is a big deal, it's important to understand the dynamics of enterprise development. For all the bad things about internal development, the one real bright spot is that you're typically working in a closed, controlled environment and thus your innovation is not bound by a "lowest common denominator" approach. Flash is nearly universally available on the desktop, so it makes a lot of sense for Internet developers to choose that over Silverlight - but those numbers are wholly irrelevant to the enterprise developer. This is precisely the reason we were able to do AJAX back in 1999, even if it wasn't ready for an Internet deployment.
It shouldn't be surprising then that most enterprises don't actually do a lot of internal Flash development. The vast majority of enterprises are Windows-based so they don't do much COCOA development either. Especially in the financial world, there is much more .NET development being done than work in either of the aforementioned platforms. And while Silverlight is often positioned as "just a Flash competitor", it is important to remember that it also brings a full, extremely lightweight .NET runtime.
Apple also intends on controlling distribution of applications through the iTunes Store, something most enterprises are not going to be cool with. They could allow enteprises to run their own application server, but that would leak in, oh, about thirty seconds. Of course, it doesn't matter nearly as much if you're consuming a Silverlight or Flash application.
While the ActiveSync announcement was clearly a big first step in transforming the iPhone from a consumer product into an enterprise mainstay, I think the availability of Silverlight would be an equally important step.