Hello to you

What is the big deal with a buffer zone between people? Do dogs have to avoid the personal bubble around people? My roommie keeps telling me that I have NO respect for personal space. I'm mean you don't see dogs respecting each other's bubble when at the dog park. Quite the contrary it is perfectly acceptable (if not mandatory) that you sniff each other's butts as an introduction! She's lucky I don't introduce myself to her that way!