But lets be honest how would you actually get to +5? Unless you did it on purpose so ur Ditto actually COULD get the boost.But thats just Eviiill...Yeah Enlong someone else said exactly that already .__.
I agree that like any other scarfer, Ditto presents opponents with an opportunity to set-up. But with just one Scarf Ditto, you basically have most of the set-up sweepers checked. I mean Jirachi has issues with AgiliGross and Scizor can't handle DD Kingdra etc etc but Ditto is extremely versatile and thus extremely valuable because it can handle all of them all by itself. Besides that, if you let your opponent get 5 DDs with Ononokuso and your Ditto comes in it's going to be quite funny turning the tables around. Yeah that's an exaggerated account and not a viable strategy given priority users and weather but I'm just highlighting the fact that it can sweep on its own since it doesn't just gain Spe boosts but any relevant Atk and SpA boosts as well which definitely makes it harder for opponents to set-up against it or anything. Not to mention why set-up when there's a Ditto waiting to kill you x_x