My sub-optimal solution to this problem has been to use Facebook for personal stuff and Twitter for professional stuff. The problem you mention about your boss seeing drinking photos or your grandma seeing racy links is easy to avoid with Facebook today, but maybe not for users who don't know about the functionality. Put your boss in a friends list that can't access your photos. Click the lock button when you're posting the link and exclude your family members friends list.
My problem is that I want almost everything to be visible to everyone, but I don't want to publish everything to everyone's news feeds and pollute them. Everyone has hobbies, interests or professions they enjoy talking about, but they don't want to burden all of their friends with those posts. If you can fix that without making me drag all of my friends to another social network, I'll use your tool in a heartbeat. I don't think it's possible for anyone but Facebook to meet those restrictions, since only they could change the way posting on Facebook works.