Yes, lot's more STEEM coming down the pipes. But also a lot more users that are going to want some juicy, juicy STEEM. Also, reverse split every few years to help with the decimal places. But you're right! Supply of STEEM is constantly increasing.
Now as for Facebook users. Let's call them ants. And money is sugar. Steemit has sugar, lots of sugar. Facebook has... well, I'm not sure really. I don't use Facebook. But here's the point... ants like sugar. And when one ant finds sugar you know what the rest of the ants do? Yeah. Ant stampede.
As for Ethereum... well. First mover is a big advantage. Look at Facebook. ;)