I cannot drink after anyone except my husband, and even then I very rarely share a drink with him. It's less of a germ issue, although that does play a part, and more about the fact that if I'm not willing to kiss a person on the lips, I'm not going to put my mouth where their mouth has been. Turning the cup or the straw around doesn't make it acceptable for me either because there's still backwash to consider. The thought just completely grosses me out.