Fandom for me is kind of like a pyramid. The bottom layer is composed of shows/movies I love, and follow religiously, but never read or write fic for, or join/start an email list for, or would travel to a con for, probably wouldn't buy the DVDs. Currently on the air, that would be shows like Lost, 24, 4400. Then the next layer. I'll join an email list, maybe even start one, but generally no fic, probably no cons (if there were any), though I'd consider it. I might buy DVDs. That gets me shows like Battlestar Galactica, Supernatural, Atlantis, HEX. The next layer up is more involvement, probably some combo of many of the things I've mentioned already. Stargate, Pirates of the Caribbean, Grey's Anatomy, House, Dr. Who, Slings & Arrows, Gilmore Girls, Firefly (which is not quite dead, so I'm including it). Then there's the pinnacle! Fandoms I spend lots of time talking about, I write fic for on a regular basis, I socialize with fellow fans, I'm a fanatic [g] Now, turns out those few special ones are both dead shows: Forever Knight and Highlander. I have no new, living, still on the air, 'real' fandoms. And I wonder if there's a fandom like that out there still for me to find? Or did I peak fandom wise? Maybe some of those second layer shows will move up at some point, or maybe something new will come along, but it's been a lot of years in between pinnacles!
I'm not sure, but I think some of those lower tier shows are just too big to ever be able to duplicate that feeling of belonging to a fandom. Mainstream shows lack the intimacy of smaller niche shows when you're trying to get to know your fellow fans. Maybe that the difference, maybe that's why there hasn't been anything new to really grab all my fannish interest. I think it's the people and the relationships that are the glue in a fandom. If I look at those layers, I realize that the one thing keeping most of those shows from reaching the pinnacle is no real interaction with fellow fans in any meaningful way.
I should probably just be grateful for the fandoms I have had, and not expect lightening to strike again. But that doesn't stop me from pondering the subject!
(Now I have that song "All The Girls I've Loved Before" in my head! Arrr!!)