Even if they bought their diploma, once they are in, they will show their true color.
The one who will be embarrassed for what he did, is himself only. A diploma is just a paper which is a written proof of his education.
But the important thing - the real knowledge and skills that he acquired to achieve such diploma. No one can take that away from you.
And this platform will just pave the easier way of detecting the veracity of their credentials. At least make it easier for the HR department, right?