Even if you aren't an early adopter, and you haven't already learned to filter by names, circles limit the conversation to the people IN your circles, or the people you think to +mention (unless you let people re-share, and then you run the risk that someone will re-share it public with your id name on it). So it's impossible to hold a public conversation with without your id name on it. In some cases that is a critical capability: you don't want to exclude anyone from reading it (including, quite possibly, people who know you under your id name). You just don't want them to be able to associate the topic with you. Which is not necessarily duplicitous or nasty; it can be as simple as bowing to social convention that discussing the normally-covered parts of our bodies with people who know us but shouldn't be thinking about those parts of us is awkward, for example....