Post rewards from posts and comments bring you 50% hive backed dollars (HBD) and 50% HP (hivepower). You need to have some Hive power to use the chain since transactions are feeless, if u have 0 you'll run out quick (like 3 comments/posts per week). It's not an issue after like 30-50 HP, no one would need more than that for their social activities so most people will get to that eventually.

Another great thing for hive's scalability is that soon we will be able to just delegate Resource credits instead of Hivepower to get RC. Meaning it won't cost them any returns (since you get curation rewards from your hive power).