More broadly, though, what Dropbox is doing is actually very much in the Apple model. Apple sells a quote-unquote “commodity” product that they differentiate with software; this differentiation lets them charge a premium.
Similarly, Dropbox is selling a commodity product: cloud storage. Apps like Carousel and these that they have acquired are software meant to differentiate that commodity, allowing Dropbox to charge a premium.
The strategy makes sense; the larger question is the degree to which consumers value non-tangible goods period.