Social gaming is the evolution of casual online gaming

Mashable last week has a good post covering the emerging field of social gaming that companies like zynga, and SGN are aspiring to dominate. Zynga etc. are the natural evolution of first gen online casual gaming companies like Oberon Media; whereas Oberon went to portals (MSN) for distribution, Zynga etc. go to the social networks. As far as I know, one of the issues that Oberon is/was constantly facing is that the margins on these games get thinner and thinner as the traffic owner (portal/social network) and the game developer ask for increasingly larger shares of the revenues.
It'll be interesting to see whether they can work out rev-share models that make it attractive enough for all parties (developer, zynga etc., social network) to work together and provide value (read: ways to kill time) to consumers on social networks. Another interesting company in this space is Bunchball which offers a suite of products to help site owners drive engagement through games, rankings and avatars.
As someone on the social network site here at Takkle I'm excited about all of these coming to market as they are developing interesting applications to plug into our network and thus serve our users.