"What's Really Behind Microsoft's New Commitment to Data Security"
Robert X. Cringely takes a stab at explaining Microsoft's latest media campaign, and he does a passable job of getting it right.
My theory: MS will focus on security because there is nothing else left to do. After two-plus decades of development, virtually every desirable feature has been implemented for both the operating system and the office productivity suite.
Bruce Schneier and other will discredit the new campaign, pointing out that security is a process, not a product, and that no amount of code review can make up for a lack of wisdom on the part of the user. Nearly any useful system can be misused by the foolish and/or determined, despite the protective measures of the designer.