these are aliases to positions of power within swil. currently, the only ones which are being maintained (i think) are presidents@swil.org, and bem@swil.org. when the holders of these positions change, send e-mail to josh at irilyth@infersys.com and tell him to update the aliases. sometimes it takes a little while for him to do this, so take care of it in advance.
basically, we maintain the presidents alias primarily for alums, who may not know who's currently president, and we maintain the bem alias because it's useful to advertise an easy-to-remember e-mail address where people can send submissions.
the webmaster@swil.org e-mail address should also contain the current webmasters, but it's a majordomo list, not an alias, so people can add and remove themselves.