Of course it can be worth the time .... if you think of it as a job & try to work for the same wage you'd normally make. Most people don't and just stick it on a site or personal blog somewhere. Rarely worth it that way Myself... hm... $200ish I think. Haven't had that in awhile tho!
The problem with adsense is that you either have 1. Huge Traffic 2. Hundreds of Adsense Sites. I think it is easier to create a hundred of them...Whatever you are earning x 100 sites...Does it sound easier?