I think that this whole process is completely natural. At this point in the VC game, investors will really only trust the most experience VCs with their money. And it's possible that soon, small VCs with small initial capital and much more focused investment strategies could garner large returns and take the stage. Or conversely, big VC funds' exclusivity, emphasis on experience, and hesitation to hire could turn them into small, successful executors of their managers' vision, and investors will put their money in new funds at the managers retire. It could really go in many positive growth directions, but the point is that this is completely natural. Big companies dominate in cycles. If they decide to hire, new VCs are ushered in, and if they don't, new firms take their place. Point is, no company can last longer than the people who run it, and no trend in the markets can exist longer than the companies that fuel it.
It's totally reasonable to say "I only want $ from big firms" because they can actually do followon rounds. As much as USV seems to be regarded pretty well, their stated preference is to only put a few million in over the life of a company - if you're expecting to build something capital intensive, you're better off going with a firm that can back you sufficiently. Even relatively early rounds ($12M at 60 pre for Uber, etc) are getting done for more than the smaller VC firms want to put in over the entire life cycle.