Shift and Carlypso are both pretty cool companies. They provide a great service for car buyers and sellers, and both are founded/run by Stanford Alumns, so they have access to the SU Post site.

BUT they need to stop using SUpost. They are making SUpost for cars practically unusable.

Technically they aren't dealers: They are facilitating sales on behalf of private owners. But usually those private owners are not even Stanford students, so they are in fact abusing the site.