This is really a fascinating issue. And it WILL define our blockchain in the future. What is really going to blow your mind is that there is not enough steem, nor will there be for MANY YEARS for each user of reddit to have 1.

That's right, there's not enough steem for everybody to have one! (Luckily it's divisible to the eighth digit, just like bitcoin).

The real answer to your question about RC's lies in something I read from blocktrades during the development and discussion surrounding RocksDB. The cost of any action, in resource credits, is relative. We can make these things as cheap as we want by increasing and expanding infrastructure. Future users , should they find themselves on a populous blockchain of millions of users, will not need nearly as much steem to post a comment as we do today.

Secondly, there are plenty of RC's to go around, currently most of it goes unused. If new users want to use steem blockchain as a social media site, they will need patronage. I delegate to new users, @crypto.piotr does, hundreds of other users do, and none of us come close to the amount of new user delegations steemit inc does. Its what we do because its necessary to treat steem as a social media site. Here's the thing though, steem is not a social media blockchain. It just happens to have one built on top of it.

Going forward, each dapp, each use case of steem will have to deal with RC's a little differently, depending on their exact case.

Thirdly, and finally, in the larger scheme of things, it is not even clear that everyone needs their own account. The @ifc competition allows entry by email, @steemnova pays out in steem but doesn't require a steem account, and other solutions are being developed (or at least I'm working on one) that allows everyday queryers to ask questions through a centralized site, which will post vetted questions to the steem blockchain with a single account. Only expert answerers will need accounts to get paid, but later even they will be able to submit their answers 'offsite' without an account.

In conclusion, there is an uncomfortability around RC's that have to do with them being very different from how we are used to interacting with the internet. @crypto.piotr's example of tyson.com clearly demonstrates this. But this is far from a problem, its actually a feature, a misunderstood feature of the steem chain, that will require some creative thinking as we go forward.

Most of the apocalyptic fears involving scaling are unfounded, and will solve themselves with hardware upgrades, some of which already in the works.