VCs, if they sit on the board, have a fiduciary responsibility to the shareholders - all of them. If they took a deal that benefitted themselves to the detriment of common shareholders, well, draw your own conclusions.
It would seem that the deal in question offered the same benefit to all shareholders: an exchange of their stock in the company for Amazon stock. IANAL, but I doubt that the fiduciary responsibility includes ensuring that the founders get to keep their brand independent, especially when it makes more financial sense for the shareholders to sell.
