Let's cut straight to the point: guilds serve as the glue of player communities in MMOs. You can pug all you want, even into end game. I've done it guildlessly before, but you never feel quite as attached to a game as when you're in a guild. There's a lot of ways guilds are described, but I've been thinking about it a bit lately, and I think there's 3 labels that might help describe them in a way to give us a better idea of what kind of social construct we're looking at. Granted, like anything we dumb down, things will be missing, there will be exceptions to the rule, mixtures of classifications, or people may want to do things a bit differently. That's all fine. I don't claim to be the sole source of knowledge in the universe, but I like to think of ways to highlight things in a slightly different way in order to maybe learn something new.
This is simply the introduction, and as such, we're going to get some working definitions before diving into specifics later on:
Family guild- This is a guild where the people who are in charge are in charge because of their relationship. This may be what some people call a "friend guild" but I think family highlights a strong trait in this guild, since friends come and go, but you're stuck with family forever, for good or bad. The idea of a relationship that can't simply be earned and just is is what separates family guilds from the other two categories we'll be using. Similarly, rules in this sort of guild probably revolve around the core of the guild's actions, not so much any specific documents. This may sound bad, but it varies from person to person; if you inherently believe that you need to be at an event 15 minutes before it start, fully prepared for the event or else get replace, and the guild leader does as well without explicitly spelling this out, you're going to love that guild. If, however, you're in that guild and think it's ok to come 2 minutes late without knowing the strategy, and then get yelled at by all the officers, that guild's going to be your personal hell. These appear in all types of games, and probably thrive the most in games where guilds are mainly there for chat purposes.
Business guild- This guild's all about getting paid. This is the guild that's about progress. It's about getting the best items, most money, and probably a heavy amount of fame. The second any of these wavers, people will jump ship. There is probably some written rules to give the business guild some legitimacy, but only enough so that there's some peace between guildies. These guilds tend to house min-maxers looking to power through the game's content then take a break or move on, if they're built to last; otherwise, they simply cannabilize themselves, die off when there's no challenge, or disband when they can't progress. Theme park games house these guilds more than any other genre, and there's a good chance they're the driving force of the game's content.
Militia guild- This is the guild that's there for your protection. Something in or about your game required people to band up against other players, either to attack them or defend them. There's a reasonably accessible structure in place that you can view at any time, and you better start reading it, since much like traffic laws, ignorance of them is no excuse for breaking them. Players have a pretty clear idea of what's expected of them and how they can gain rank. Even if it's fairly similar to a family guild, the rules will be spelled out rather than assumed. While the business guild's looking to get the most out of the game's mechanics, the military guild's looking to get the most out of people, either by coherence, domination, or manipulation. Some militia guilds may lose members when they fail to protect them, but the guild's structure gives hope to its members, making them believe that there must be something they can do to fix it. Military guilds will be found most often in sandbox games with heavy pvp, but also RP servers where non-RPers make it necessary to form some kind of structure and meeting places away from prying eyes.
These are just the general idea of the classifications. Next time, I hope to flesh these out the familiy guilds a bit- how they aren't just "friend guilds" with a different name, some of the good, the bad, and heck, maybe even give some more solid examples of them ;)