I ran a clad called |K!D|. Stood for Killas In Disguise. We were B.A. back in the day. Played Day of Defeat. I had some of the best snipers in the game. Fell apart after I quit the game.
I was a clan leader at one time but have since backed out of the gaming scene a great deal. Now just game casually when the time seems to be in my favor.
Back when I was a heavy PC gamer, I used to play Unreal Tournament 2004 and was co-clan leader of >BIG< (Big Idiotic Gamers). We had an active TeamSpeak and one of the most popular servers on the game, featuring team games, assault and racing maps. Those days were just incredible, spend 2-3 hours at sixth form, come home and switch on the PC and game for around 12 hours non-stop. Running a clan was fun at most times, we had an active forum, a good website, alliances and played in a few tournaments.
Then you have to weigh in the negatives, which include; administrating a server, looking after clan members, taking clan meetings, clan drama and clashes, and much more. If you have the patience and dedication, then running a clan is an extremely fun experience and can improve your enjoyment of the games covered. But be prepared for the downsides, should they arise.