Guilds

Guilds can be founded at guild master NPCs at major towns for 5 gold, and have a maximum of 200 members. There's a tag below the name that you can turn off in the preferences, a member list, and a guild chat channel. There don't appear to be special guild features apart from that.

TouchArcade
A TouchArcade community guild, founded by Eli, currently more or less full. TouchArcade forum thread

Arcadians Touch
A guild originated early April for the Touch Arcade community in the upcoming games O&C forum.

Arcadians Touch was founded by the member Creepshow.