It went to the 'allmit' list (http://mailman.mit.edu/mailman/listinfo/allmit) which goes to "all current students (including incoming freshman and graduate students, special and cross-registered students) and all employees listed in the MIT directory or with SAP status=active" which is upwards of 22,000 people.
Right and evidently whomever shared this did not want the other 21,999 people seeing that they had posted it to their blog. So they shared it anonymously.
Either that, or they don't have a blog. Pastebin is an easy way to share an e-mail or some other text if you don't have some other method of publication easily available.