Banning the platform most of your users are using doesn't sound like a great idea to me. There's enormous value in eating one's own dogfood (and stuff running in Chrome is an entirely different kind of dogfood than stuff running in IE, on Windows).
That makes a lot of sense, as Windows boxes are not really good for web development, but I really hope they still test everything on Windows, extensively. Even though their software is web-based, there's still difference in behavior on different platforms.
To a certain degree this is sensible. It will probably make them safer in the short-term.<p>Ultimately though this is just a TSA level maneuver. It's reactionary, short-sighted, and imperfect to a degree that is likely to make it nearly useless.<p>Security is a meta-property, for organizations as well as for software. You can't create security in software as a line-item feature. Nor can you create security in a company by using, or not using, a particular tool. Security ultimately is an overarching endeavor. If google is serious about security they need to approach it that way. The particularly dangerous failure mode for google's recent actions is that they think they've made a serious security enhancement (at best it's incremental), they become complacent, and then they get owned harder than before.<p>Hopefully this is just a teeny, tiny aspect of a larger security initiative, but from the outside it's difficult to tell if that's the case.