Posting to hopefully help next years candidates,
I applied to 11 and by the end I had messed up 2 applications. I was purely exhausted and it showed. I applied to 5 reach programs, 5 reasonable programs and one safety program as I had done all my rotations except 3 there this yr. I received 5 interview invites and 1 waitlist. 1 reach program, 3 reasonable programs and 1 safety program, with waitlist from one other reasonable program. I matched with my reach program!!!!!!!
Overall, I was happy with the amount I applied to and while some may look at it as a waste of $$ im truly glad i applied to as many reach programs as I did, because I got one. I would have been disappointed in myself for not at least trying. However, I wish I started apps sooner (I waited until after Midyear and felt so rushed on all of them.) I made a mistake one 2 apps, 1 reach and 1 reasonable. i feel like that is the ONLY reason i didnt get an invite to the reasonable program. My waitlist was a reasonable, and it was: if the program didnt match phase ii they would reach out to me if I chose to be on the waitlist. i said yes because for added security. I will never know this for sure but I believe they waitlisted me because they do rolling invites and had already invited their max # before getting to my app which i submitted the very last day before deadline. again, should have started earlier.
I agree that 6-10 is probably appropriate and even that feels like a lot, but keep in mind it depends on the places you are applying. Are you applying to competitive large academic medical centers? then do more than that. And definitely do a mix of programs. i chose all teaching institutions, but did 5 AMCs, 2 large teaching hospitals, 3 medium-to-large teaching hospitals and a pediatric hospital. geographically my AMCs were spread among the midwest/NE, since I am going to school in eastern portion of midwest and i am from the northeast. All other hospials were ones I was familiar w because they were either from my hometown city, the city I am currently living, or my SO’s hometown city. All of which are medium to large metropolitan areas within the eastern midwest and western northeast.