Yup, I don't feel comfortable with anyone but me reaching into the racks and pulling out snakes. If someone were to get my snakes out while I'm not there, especially someone who is a friend of a friend or something like that, I'd go off...
For me it's not so much risking transmitting anything between snakes. I'm confident that mine are all healthy (knock on wood). I would worry that:
a.) the person wouldn't know how to handle snakes properly and could potentially hurt my animal.
b.) the snake could bite the person, causing them to freak out and possibly injure my animal.
c.) if I'm not the one putting them back in the rack, I don't know that the tubs are slid back in properly and would worry about my snakes escaping.
but most importantly,
d.) that's MY stuff and you have no right to touch my stuff without asking me first. If you're going to be disrespectful enough to get into my snakes while I'm not around, what else might you be getting into? No thanks, you can just find the door and don't bother coming back because you won't be welcome...