Whales want this platform so succeed so I think it's highly unlikely that they would just hoard all the tags only to sell them later. Some of that would happen, but there are lots of words in the world, they can't buy them all. There will be plenty of them left to normal users. And the tag won't become valuable just because of the name, the owner has to make an effort to get people to follow it. Worth of tag comes mostly from the amount of users who are following it, not from the name.

Without ownable tags/steemrooms, how would you exclude unwanted users from groups? I think exclusion is very much needed feature, groups can't function properly if anyone can join and do whatever they want.