[fpgeek]

Even you aren't cross platform personally (e.g. you don't have a Mac and a PC at work or an Android phone or ...) Dropbox lets you share files and folders with other Dropbox users. Unless you're confident that you'll never want to share with someone on a different platform (which only sounds realistic if you never want to share at all), that's important even if your personal environment is homogenous.

I'd guess that most Dropbox users share something (though I haven't seen statistics on that) so they are probably less threatened by vendor-specific solutions than you might think. I suspect Dropbox is more threatened by services like Amazon Cloud Drive (especially since Amazon is an infrastructure provider for them) than they are by anything Apple or Microsoft has planned.

[justincormack]

I don't use dropbox for sharing at all, and suspect I am not alone. Generally use Google docs fir that. Dropbox just for replication to my devices.