I happen to use 7 / archlinux / Os X almost equally. Of course my comment was trollesque, but an affirmation like "Microsoft ... tends to be very good about security updates" is not realistic. Time elapsed between exploit discovery and patch proposal to the user is everything but short. And If every website with a security issue was to answer to the congress, well it would not do much else. Plus, given the money Microsoft spend lobbying, I doubt very much that in a similar situation they would have to answer to the congress. Dropbox just seems to be a marked man.