The actor who played Eko (Adewale Akinnuoye-Agbaje) didn't go on to be in any other projects until recently. I don't know what fueled his departure from the show but it seems they got rid of nearly all the tailies. I personally was relieved to see him go, I couldn't stand his character and felt like his story lines took away from the rest of the show. Who knows, if he stuck around maybe I would have changed my opinion on him. I had once felt the same way about Locke.