Some people have tags that say random things, or things that are meaningful only to them, or an injoke instead of using one of the obvious things. I find that impossible to navigate and loathe it, find it not funny and wish the practice would DIAF. Of course it's their journal, so there's no way to prevent it, but I feel this encourages behavior like that, because it might suggest that tags that aren't transparent and useful for others might still allow others to find say all your fanfic, even if you taggged it "gnarglgnurps" instead of "my fanfic".