When someone thinks they're really clever because they make half their post or Tweet a hashtag. So they do it all the time.
Real life instances of "Hashtag's Disease":
I was home two hours late for curfew. Oh wait, #WHYDOIHAVEACURFEW
I AM IN BED SO EARLY AND IT FEELS SO NICE! #igothomebeforemyparentsdid #notabigdeal