First, to Apple's problems. I supposed you could say that there's an inherent security question, but increasing network security isn't the solution. The problem is that increased attention on Apple products have shown many fundamental security issues. Because the company has tried to create a false image of their products being inherently safer than Windows-based PCs, which has led to many Mac users, who should know better, not installing elementary antivirus protection. IT departments, however, won't be so forgiving and will be suspicious of the products as clients.
The much bigger Apple issues for IT, though, are cost and support. The Mac products are budget breakers compared to PCs, and to freely support both would take increased costs, the major reason why many corporations largely phased Macs out in the first place.
As far as Microsoft's status as a security trend setter, it doesn't have one. Identity management as security technique and technology goes back to the early 1990s, if you don't want to count implementations that date back to mainframes. At least in 2006, Gartner had an identity and access management summit, which means that the topic was in serious consideration by enterprises before that.
This is an area where Microsoft is playing catch-up, and it must if it wants products that will work with the existing security infrastructures at major corporations. So the company hasn't opened a door for Apple. Microsoft is simply inserting its foot to keep from having the security door slammed in its face.
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