Theory: They're dumping to lower the valuation of Dropbox for a possible later acquisition.
"Well, you could sell to us, or we could put you out of business."
"Well, you could sell to us, or we could put you out of business."
I know there have been stranger acquisitions by Google, but I just can't think of any benefit to Google if they were to purchase Dropbox.
Do I think that is worth what Dropbox would cost? Probably not, but Google has heaps of money and hey, what would I know?