I only ever see spam in tags - I've heard that some folks get ask-box spam, but I haven't ever seen any of it. And almost always in popular tags within a fandom - e.g. in the tags I spend time in, the Korra tag and the Steve Rogers tag will get a bunch of spam, but not the T'Challa tag or the Lin Beifong tag. It might just be that I spend more time in tags than you do?

By RP I mean some organized role playing games, but mostly independent roleplayers - people who make a tumblr for a fannish character and then post to the tags soliciting either asks for their character or other independent RPers to have conversations with. A lot of the requests are specific - e.g. a Natasha looking for a Clint or multiple Clint(s) to RP sex scenes with. Since I'm on tumblr for fanart, the multiple posts of ask box RP or RP threads annoy me in tags :)