Disgusting or not?

[RAMd®d]

Depending on who you ask, it's a matter of contamination, sanitation, and intimacy/familiarity that's at question.

If someone got the last bite, stick, or piece of some morsel that one wanted, would they accept it if the other person removed it from their mouth and offered it up?

For most of us this is probably more about boundaries and circumstances than sanitary practices. Putting the spoon back was disgusting.

If the Margarita Girl offered me a sip of her soda, I'd be inclined to accept.

I wouldn't want to be rude.