.wiki I’ll give you one guess what it’s about?
You guessed it (at least I hope you guessed it)
I presume it’s safe to say we’re all aware of wikipedia? Personally I use it on a daily basis and I’m sure if you do a search online you’ll see a link to wikipedia at some stage. So if wikipedia exists why would you want your very own .wiki domain?
Simple it’s your wiki to do with what you want. If you’re a brand does it make sense to let your users help out each other? If you’re passionate about a topic say baking or programming doesn’t it make sense to have someplace collaborate with people?