I think the main issue is identities that are not voluntary, like the ones we are used to getting from the state. If you could have 3-4 selfs online, perhaps you wouldn't be so worried about getting the one account perfect or making a mistake. Online identities affect our state given identities and many people are a bit nervous about it with good reason.
That's an interesting way to look at it. Everything online is public to a certain extent. But people seem less worried about it than they used to be. I remember my elders trying to tell me that swearing and other "unprofessional" behavior on Facebook would hinder me in a job search, which hasn't happened yet (that I know of!).