Earlier quoted context omitted.
Dropbox wasn't a trivial engineering problem. While making facebook for a couple thousand users isn't too hard, scaling it to hundreds of millions was no trivial feat either.
I was under the impression Dropbox is a UI to Amazon S3. I use them and don't mean to deny it's a slick package. But I could duplicate the entire thing in about a day with inotify and rsync. The scaling is mostly on Amazon. That said, I must point out that the scaling issues all of these super modern "change the world" companies, such as Twitter and Facebook, have are purely for the purpose of centralizing power. It'…
No, you could duplicate a narrow piece of Dropbox's functionality in a day. You could not even get anywhere near duplicating the product and the service in anything less than months.