I don't want to mess with deposits for something that really should be a standard amenity. And I do not want to ask people to bring their own phones. Our bookstore sells pre-paid phone cards to make long distance calling easier. At the end of summer conferences, we remove the phones. Thus far we still have the same number of phones as when we started.
Some guests use the same phone jacks for their laptop computers.
I would love to hear more about how other campuses are tackling this problem. Our students provide their own telephones in the residence halls during the school year, and take them when they move out, since the phones are each student's personal property. Adult groups are told that they may bring their own phones along, and we provide them with the phone number for that room. I haven't been charging back for the groups' use of these telephones, but since I'll probably need to replace some next summer, I will probably start doing that. However, we do still have at least one pay telephone in each dorm, and so many people are carrying cellular phones these days, that we haven't had any complaints.