I'm talking about FTP, SVN or similar - access to a clients website files.

Either the client themselves (penny pinchers!) wants to modify the site, or they've contracted some other developers (again with the penny pinching!) to do some additional work on the site.

How do you deal with it? Do you disallow other people access to sites you've developed? Do you reluctantly agree? If so, how do you circumvent issues that arise with multiple people working on the same site?