Someone over in the Google forums posted this link:
https://groups.google.com/forum/#!topic/google-plus-developers/dg9tkCPQ3TE
Basically, it is Google saying they are closing their Google+ Developers support forums in favor of redirecting their customers and end-users over to StackOverflow.
Clearly, there is favoritism here. It's not just StackOverflow having good SEO.