My American audience isn't going to know k-os very well. k-os is a Canadian "alternative hip-hop artist", according to his Wikipedia page. I wish he was known better south of the border, because his sound is soulful and innovative.
This song, which won Single of the Year at the 2005 Juno Awards (which, for those unaware, are kind of like the Canadian Grammys - and this was the first time a hip-hop song won that award), referred to the crab-in-the-bucket syndrome. Basically, if you throw a bunch of crabs in a bucket, the mob will work to pull down anyone who tries to escape - a metaphor for someone trying to escape a particular socioeconomic situation.