Let's say I'm walking on the sidewalk in front of your house and decide that I want to talk to your neighbor. Do I walk my ass into your backyard and yell over your fence?
No, I don't.
So don't walk your ass into my cubicle so that you can hang over my wall and talk to the person next to me. It's rude, it's disrespectful of my personal space and it's a little bit awkward especially when I have my headphones on and am staring intently at my screen and don't realize you're there until I reach over to open my top desk drawer . . . and find my hand in the top of your drawers instead.