Nobody is forcing your to post on G+ or Facebook, but as large companies, their policies have ripple effects. If we accept what they do now, what will things be like in 10 years?
At least in the US, there was already political chatter about requiring everyone on the Internet to have trace-able identity, and maybe using FBConnect or Google logins to do that.
Regardless of your views, large companies implementing 'real name' social networks makes it closer to a reality. The closer we come to basically having a 'switch' that would allow politicians to turn on such functionality, the more likely it is for them to flip said switch.
At least in the US, there was already political chatter about requiring everyone on the Internet to have trace-able identity, and maybe using FBConnect or Google logins to do that.