<p>Ignore cobrat’s last paragraph. The part before that makes some important distinctions. At some colleges, there is no officially sanctioned Greek system, but participation isn’t prohibited. At such places (and it sounds like Harvard is like this; I know Yale is), the Greek organizations aren’t really “underground.” They still may receive some punishments from the college–such as being banned from activities on campus (this happened to Deke at Yale). There has been growing interest in Greek organizations at Yale (and I guess at Harvard), despite the residential college system, which is supposed to obviate the need for Greeks. In my opinion, this has happened because the higher drinking age eliminated many social events with drinking that used to occur on campus, and Greek organizations have filled the gap with unsupervised underage drinking events. I don’t consider it an improvement over the old system.</p>
<p>At some colleges though, not only are Greek organizations not sanctioned, students are prohibited from joining them. At such places, fraternities and sororities really do have to be underground. This has been an issue at a number of high-profile LACs.</p>