One of the common horror stories we hear from prospective clients is that their current/old agency is threatening to remove links if they leave. We would never think of doing this, if for no other reason than it would be staggeringly unprofessional and immensely time-consuming. All work conducted during the project would have been paid for and would remain in place*, including all links built.
Furthermore, we never use link networks or place links on sites we own or control. This means that link removal would only ever be done by the owner of the site, or if for any reason a client asked us to remove a link (although this could only be done at the discretion of the site owner).
* From time to time, links created by AMG may be removed for various reasons by the site owners, for example, a site removing old content during a redesign or being permanently deleted (these things happen even to the biggest sites). While we take care in choosing where to place a link, we cannot be held responsible and will not guarantee they will not be removed by a third party.