I’ve always perceived Dropbox as a transit place, a location where one drops a file waiting for somebody else to pick it up. I’m also using the free account, my motivation being that I have too many other online storage places already. I did see another article on Techcrunch, saying that Dropbox have raised $ 250M in funding, very impressive.
But I do think that this article makes an interesting read: http://www.forbes.com/sites/davidcoursey/2011/10/18/how-dropbox-will-die.