We continue to participate in the coordinated collection development efforts of SUNY Libraries. The "rule" is: If a title is already owned by three or more SUNY schools, our policy is, we will not purchase that title, but select a comparable title in the same subject area.
Our collective goal is to diversify the SUNY collections and to view all SUNY library collections as one SUNY library collection. If you feel that the College Libraries should purchase a particular title even though it is held by 3 SUNY libraries, just send your rationale (e.g. needed for specific assignment) to your library liaison and your students' needs will be considered as we make purchase decisions.
If we discover we failed to purchase a seminal title that we really should have for our collections, we can always buy the book at at later date (and usually at a lower cost). We routinely check what students borrow on Interlibrary Loan to see what we are missing. In the long run, it is less costly to purchase a book that get high use, rather than rely on Interlibrary Loan. The "rule of three" is more like a guideline for coordinated purchasing, rather than an unbreakable law.