what happens if the price of Steem reaches that of Bitcoin, or even passes it? With millions of Steem coins in circulation, do you really think that an average user is going to invest any money to buy .5 Steem, to gain only .001 MV worth of influence?

Yes. If the price goes that high, who wouldn't want vests that gibe you 250% interest rate per year on steem.

You have to remember that steem is being mined constantly, with the price going higher up this would mean that even small fish now will give out good rewards to posts in the future and the daily reward pool would be worth a lot more $ than it is now. With early investors having powered down and the holding of vests having been distributed more evenly towards more accounts, I can see this being a good possibility of the price per vest or steem going that high.