it should be in all whales interests to support minnows as much as they can, since the growth of steemit also means a growth in their stake as a whale. the bigger their stake, the more they stand to gain. if users leave the platform, and all that remains are the whales, their big chunks of power would mean nothing anyway.

of course, you could also argue that they had the foresight to invest early, etc. it's definitely not wrong for them to upvote themselves only, but the question is - is it the best course of action for them/steemit?