Wow. Where to begin. Not with Microsoft, but with some of the comments here.
Microsoft did a smart thing. And, it's unfortunate they had to do that, but they did it because people are, well, people.
Any large corporation has issues with some people abusing company resources, whether it's spending all day surfing the Web, padding expense reports, showing up late and leaving early, or a number of other things.
Microsoft has a Macintosh Business Unit (MBU) that can still buy the necessary Apple products that Microsoft will support, whether Macs, iPads, or whatever. That hasn't changed, if you read the article.
From the article, I'm picking up that Microsoft wasn't restricting Apple purchases from other areas of the business (that is, areas other than the MBU), until now. And, they still aren't restricting 55% of the company, which means a lot more than the MBU can still purchase Apple products.
I gather that with the (at the time of the memo) imminent launch of the iPad, Microsoft was concerned about employees purchasing devices that wouldn't be needed for company business. Rather than react and spend a lot of time and resources trying to ensure that funds are wisely spent, they nipped it in the bud.
There's nothing wrong with what Microsoft did. The problem is employees that will spend money unnecessarily. That's not a Microsoft problem. All large companies have that problem.