Robots on twitter who follow you as a result of you repetitively talking about something (bots) , they tend to unfollow you as soon as you stop talking about their topic. Therefore they are never loyal to those who they follow (whore). Hence whorebots. They are for advertising.
I talked a lot about my iPod and picked up a whorebot called iPodsforyou on twitter, it unfollowed me next day, bloody whorebots!