Very good points! People around here seem totally oblivious to the fact that mainstream exposure is going to bring a bunch of stuff into Steem that we haven't seen yet: advertising, political propaganda/campaigning, and like the OP pointed out, narcissists. Every time I bring this up, I get a response something to the effect of "I hope we can keep that stuff out!"
But the reality is that we need all of it! Advertising and politics will bring much-needed money and finally silence the "ponzi" criticisms, and as @anduweb points out, the narcissists will bring their worshippers along as they go through their massive and spectacular flame-outs.