Pathfinder tabletop game that Pathfinder Online is based upon, you know that you need to have grouping. After all, the former is all about bands of adventurers exploring the wilds. So it's fitting that the most recent developer blog is all about the game's methods of managing groups and playing in different numbers. And this isn't just a matter of parties or solo play -- at the high end, players can be running entire kingdoms as a social unit.
Solo play is meant to be somewhat discouraged, as the blog notes it will be a much more difficult road for a dedicated lone wolf. Parties will be the next step up, holding an undetermined number of players (the working target has about 24 players at the high end). Above those are chartered companies, settlements, and as mentioned, entire new player-run kingdoms. It's going to produce some interesting dynamics to have player organizations in such abundance, but the developers seem to have some confidence in their initial designs.