Your claim seems to be "dropbox is profitable, therefore Google should buy it" - Ben and Jerry's is profitable but I don't see it as a potential Google acquisition.
Dropbox is built for a time when the desktop is still relevant. Google are gearing up to overthrow that paradigm. Dropbox doesn't have a clear link to the web at large, or to search, or to the creation and indexing of content. Those are the attributes I associate with "google acquisition fodder". Compare tineye.
If Google do buy dropbox, it'll be as a talent acquisition and/or so they can leverage the userbase into a chrome OS based solution.
Did that happen?
edit: Just read some of your comment history. So why do you think the offer was made?
edit2: I mean, ok, say I'm google and I'm thinking about buying dropbox:
We can index the user's documents and provide a kick-ass search interface as a product feature, as well as pushing existing products like google docs. Indexing will also feed into advertising across the board, if the user's logged in to their Gbox we can make any adverts they see relevant based on the contents of their own files, which will potentially create an awesome relevance to the user thus increasing CTR and revenue.
I guess that's a pretty convincing argument actually...