jimbeetle - 4:24 pm on Sep 3, 2007 (gmt 0)
Best practice is to return what it actually is. Though most SEs treat a 404 (page not found) and 410 (page gone) response the same, I'd go with a custom 410 page telling the user that the listing no longer exists. I wouldn't use any redirection as a large number of pages redirected to the same one, such as the home page, can either look spammy to or at least confuse bots. Include at least a link to the home page or, if programatically possible, a link to a similar job category.