Apartment List just 'elaborated': http://blog.apartmentlist.com/webby-strategy-elaborated/

Note the distorted use of page view statistics to help put the explanation in context. If you have a look at Alexa you'll see padmapper gets substantially more traffic than Apartment List.

For the record I don't think they've used a bot, but I do think they've used outside(paid) help to generate votes.