A diploma mill is an institution that pretends to be legitimate but actually is a fake, sells diplomas, and misrepresents itself. Recently, many have become concerned with the apparent proliferation of diploma mills (Carey, 2010). While it may be easy to root out diploma mills, another approach is to evaluate an educational institute by what it is and what diploma mills are not. Here is a list of what diploma mills are not, and what legitimate educational organizations are:
Diploma mills are not organizations that:
are accredited by one of the regional accrediting agencies;
are schools with one, infrequently changed address, website, and phone number;
require a well-documented and widely published admissions process that normally does not allow student admissions at the last minute with unbelievable offers;
offer courses and programs that can only be completed in what most would think is a reasonable period of time, based on some established criterion such as the course/Carnegie Unit;
permit, offer, and encourage interaction among students and between students and easily identified faculty;
have a clearly established and rigorously followed process of faculty oversight of the curriculum, usually by a curriculum committee;
rarely, if ever, provide course credit for life experiences, or work-place responsibilities;
review the credentials of instructors and permit only those to teach whose qualifications have been carefully screened; and
establish a brand, a visibility, even a prestigious reputation in the academy of similar institutions.
This list could be expanded. Without doubt there needs to be research about the concept of the diploma mill in a distance education environment. There is much to be learned, and much to be prevented.
And finally, we should not use double negatives—diploma mills love confusing language so we must be clear—diploma mills are not acceptable!

