On Google+, you can quite reasonably follow thousands of others and still keep track of everything your friends and family post, plus the occasional random.
Following people implies at least a very basic interest in what they have to say. You can't follow more than a few hundred people and still keep track of what they're saying (and that's with a low average post count). If you're following thousands you're either a bot or just racking up numbers in which case the follow relationship is totally meaningless.
I would have agreed with you once but now I think that, to a certain extent, maintaining social connections can be a bit like physical fitness. I could say you can't run under a 4 minute mile or a single race of > 100 miles, yet people have and do while almost none of us on HN ever will.
My change of heart has come after 5 years of using Twitter. I could only follow 100 people well at first but somehow it crept up and up. I've had quite a few culls and now I'm at 1000 people I follow and whenever I go through the list I recognize almost every name. It's not quite a 4 minute mile but I've been able to get at least a feel for those 1000 folks and know they're ones I appreciate following.