[tvwonline]

Right now, a large number of Android sales are Samsung devices. Samsung is very profitable. [1]

There is a risk to Google that if there is not sufficient diversification in the Android market then Samsung can do what they want - including in an extreme scenario forking away from stock Android and creating their own lock in ecosystem to go up against Apple. (this is an extreme scenario - but I don't think its impossible)

Remember non-tech savvy people may just enter a store and think do I want an Apple or Samsung phone/tablet.

I also wonder if the real purpose of the Nexus devices are to help get other devices makers up to speed to compete with Samsung.

[1] http://www.asymco.com/2012/11/14/google-vs-samsung/