To give you a breakdown of my current guild, we are middling on raid content (a few bosses into Serpentshrine Cavern), we raid about four nights a week for three to four hours. We are made up of IT professionals. Police officers, electricians, plumbers, stay-at-home parents, truckers, and even our very own rock star who is putting down his raiding life to go on tour with Incubus in Australia. We have people from New Zealand, China, Europe, Canada, the US, and I'm sure a few other places, and we are varied in age from 15 to 50, not to mention that I think we have one of the highest girl gamer populations of any guild I've ever been in. We are, for the most part a pretty tight crew, who get along get through content, and mostly keep away from each others throats.
One of the things that has worked out really well for our guild in particular is the recent addition to the World of Warcraft of guild banks. This is a feature that many see as long overdue, and allows guilds to hoard their items together in a central place for all to see and have access to. In the past we had a number of alts that the officers took care of, who kept items for their specific classes, or purposes (i.e. raid bank, crafting bank, etc). This of course, was an endless headache, because we either had to wait for a specific person to login to get an item, or we had to share out login info which is chalk full of it's own problems. But now all of that is behind us, the officers are granted access to different levels of the bank, everyone can deposit, and with the implementation of the new feature of "repair" money, where certain people can use the money in the bank to repair their gear, it makes it even more friendly to raiding guilds.
Blizzard has been one of the leaders in the games I have played who are working towards guild content, when they added voice chat to the game a few patches back it removed the need for outside ventrilo or teamspeak servers that a lot of guilds used (though I do think those services still offer more, they aren't necessarily needed anymore). Now with guild banks, and possible whispers of guild housing in the future, they are constantly adding more to the game to make life easier for people who run guilds, as well as the general populous.
However one thing that game designers will be unable to ever code out of the game are problems with guilds. There are a myriad of them, from bitchy players, loot whores and ninjas, and corrupt guild leaderships. Over at our sister site WoWInsider, they have a column dedicated almost entirely to guild drama and achievements and it is one I often get a good laugh out of, having been a part of a solid guild for almost two years now. Though I suppose a lot of it is just simple human nature, and the easiest way to look at most guilds, or collections of guilds is the same way that really crap hollywood movies have been looking at high school for years now. You have your jocks (the raiders), the popular kids (people who post on forums and are known guild or server wide), the outcasts (the guildless, or pariah's within their guilds), and the parents (guild officers anyone? You can't think it's any different than babysitting some days).
I would like to see some more advancement in future games however to help out guilds, to make it easier to get running. Things like guild banks, in game voice chat, and guild housing are a great start. They make it easier for the guild to work together, and also for guilds to be accountable for themselves. When everyone can see who has access to what, and who is depositing/withdrawing from banks, thieves and ninjas get caught out quite a bit sooner. But what other features could be added? One thing I would love to see in WoW would be Raid IDs that are open across a guild, often times we have problems filling Zul'Aman or Karazhan clears later in the week, because so many people are saved to this or that raid. But if you could make it possible to hop into any guild run, then you wouldn't have that problem. Certainly this would mean that more people would have access to more loot (you could run partial sections of any dungeon a number of times), but I'm sure with some sort of progression tag where you cannot enter an instance who is on boss one, when you have cleared up to boss forty three, or whatever, it could be avoided.
Another interesting feature would be the ability to share information across guild members, where by clicking on a players name in your guild tab or linkshell menu, you could see who has been saved to specific instances or bosses for the day, and maybe even see if anyone has similar quests to complete. Using addons like Questfu, you can see who in your current party is sharing a quest with you, why not expand that even further and add it on to guilds. No more spamming guild chat with "I need three people to help me kill X dragon". You could simply click on the quest and bring up a menu of who else in the guild needs to kill that dragon. Or when you're in a heroic instance or raid, be able to see who is saved so you don't have to pester them with a back and forth asking if they could come lend a hand.
Along the same vein, being able to see what characters have what recipes for their chosen trade skills would be endlessly helpful, currently we keep a (sort of) up to date list of people's skills and their recipes on our guild website, but a I have to admit, it can be a bloody pain sometimes having to alt tab out and look through a list as long as my arm to find out that no one can craft that epic helm I've been looking for, for weeks. To be able to simply type the item name into some sort of guild database (ok ok, I could code something like this for my guild, but I'm far too busy playing six different MMOs, writing about them here, and working), and have it pop up with who can craft it, and if they are currently online. Maybe even go so far as putting yourself in a queue with that person, letting them know that you're interested in a recipe that they have.
Of course if anyone from any of the game companies is watching, you can always drop me a line, I have hundreds of other ideas, then I could just quit that pesky job of mine and come work for you, filling your beautiful minds full of my ideas.
I suppose though, at the end of the day, a guild is a place we all need or don't online. Some of us are happy just running around doing our own thing, where others require structure and tireless group of people to run content with.
Guilds are here to stay, and love 'em or hate 'em they do exactly what they are supposed to.