I cant stand bags where I cant have them over my shoulders!!! I tried hooking it to my arm the other day since I was too sunburned and it bothered me so much!
I used to be a shoulder bag only girl, but then my shoulders couldn't take anything on them from 4 years of lugging a huge backpack around in high school, so recently I've had to switch to the crook of the arm. I've found that carrying a bag on my arm is most inconvenient when shopping, but aside from that I don't mind it too much.
Usually over my shoulder, unless it's a small bag and then I might carry it on the crook of my arm. I take metro, so I'm used to wanting to have my bag on my shoulder, where I can keep it safe.