[probably_wrong]

Leaving aside the reasons mentioned above about why being anonymous is really important, there's another reason: money.

I think it is wildly accepted that major social networks are full of ghost and/or inactive accounts. If companies cracked down on those, everyone would see that their numbers are not accurate and their valuation would take a big hit. Some CEOs would lose their jobs for sure. So it is not in the big networks' self-interest to change that.

You could make a network from scratch, were identity is baked in from the start. But who would sign up? If Google+ thought us anything it's that people really hate giving their real names (and rightfully so, IMHO). Sure, some services managed it, but they are not as influential as the big ones.

So no new service has the network effects to pull it off, no big network wants to lose money on doing it, and users don't want it.

[coldcode]

There needs to be anonymous accounts on the internet because of safety. However someone you need to be able to derive a system that permits you to validate you are an individual internally to the system, but also allow for anonymity externally. This way the anonymous speaker is protected, but you still know that it is a real person, just not for you to know who. Of course the anonymous person could be a bad actor (whatever you define that to be) but at least its not a bot.