If you look at their foray into photos and the way they talk about their service now, Dropbox is becoming a lifestyle brand focused on your personal data.

Meanwhile, the mobile e-mail client that the Mailbox team built is so cool that it convinced about a million people to let Mailbox store a full copy of their e-mail archive ... in 10 weeks.

That kind of strategic value means it's smart for them to swoop the product and team up RIGHT NOW, even if they had to pay a premium to do it.

I don't know about "very clever", but if you look at Dropbox as moving towards an iCloud-like service where its more than just data, it make sense. But it sounds a lot like a talent acquisition that comes with a nice mail app that probably has some similar technical challenges to the things Dropbox already does well. Seems like a good way to kickstart a Dropbox email platform.

I think that Dropbox wants to be the company on the internet where your stuff "is" and email is probably part of that.