Brain dump on the word "fandom"
"Fandom" is a made up word popularized on Tumblr. Its a blend of fanatic and kingdom and it sounds really weird when ppl in real life use it. The word has become part of an unofficial dialect: "Internet English" and is used commonly in the sub-dialect of that: "Social network English." It is most common in the subsub dialect: "tumblr english."
The reason its weird to hear "fandom" used in sentences in the real world is because it isn't a part of that dialect and is being borrowed. It's just as weird as hearing a foreign way to refer to a grandparent. Opa, Boompa, G-pa, grandpa, and Bumpa all refer to the father of one of your parents but if you were having a conversation and someone says "my boompa bought me ice cream," unless you also referr to your grandpa as a boompa (which is unlikely, I stole the word from Brian Crane's comic, Pickles) it will strike you as odd.
There are some people who use Tumblr Vernacular English in the real world, having learned and mastered the dialect. These people likely only, or predominantly socialize with other Tumblr users.
This is all of course speculation and I would love to get some info from people that actually study linguistics (specifically dialects or morphology).