I have only formed my own guild once, and it wasn't in World of Warcraft-- a group of people I grouped with in another online game thought "Silver Monkeys of Death" would be a good name for a guild, and so, strangers though we were, we paid the fee and grouped up. It lasted about a week. The only way I can see a guild really succeeding is if you have a few people who know each other in real-life to support it-- if you can get a chain of about 10 people who know each other really well (as in friends of friends), then you're on your way to getting a good guild rolling.
But other than that, I can't really see it happening. I'm not talking about guilds who move from game to game-- I'm talking about guilds that are supposedly formed by people who've met each other only in game. Is it really possible for a group of people who have only met each other in game to actually form a full-fledged raiding guild?