It's easy to see why you'd want the option with a public account. You may not want an ex or former friend commenting on everything you do, for instance. And if you've ever seen the creeps that tend to post leering comments on women's Instagram selfies... you get the idea. This won't prevent sketchier types from viewing your feed, but it will relegate them to passive observers.

Instagram has been expanding your control over its experience lately, including choices to mute people you follow and an experimental 'do not disturb' feature. While they cover a range of subjects, the theme appears to be the same: Instagram wants to eliminate the content that might drive you away, whether it's harassment or too-frequent notifications. Instagram is now a mature social network with over a billion users, and it's just as important for the Facebook-owned service to keep users as it is to reel them in.