Google announced last night on Google+ that they have removed their naming restrictions, preventing you from using nicknames and pseudonyms.
So if you wanted to use the name "rustybrick" because you didn't want to use your real name, for privacy reasons, you can. If you wanted to use "GoogleGuy," you could.
This was how things were back in the day, very few people 10 years ago used their real names. Everyone used nicknames within the social network or discussion forum they participated in. Now, it is less common.
Google+ is now allowing for it because, well, I guess they want to solve their YouTube comments problem. Here is the post:
When we launched Google+ over three years ago, we had a lot of restrictions on what name you could use on your profile. This helped create a community made up of real people, but it also excluded a number of people who wanted to be part of it without using their real names.
Over the years, as Google+ grew and its community became established, we steadily opened up this policy, from allowing +Page owners to use any name of their choosing to letting YouTube users bring their usernames into Google+. Today, we are taking the last step: there are no more restrictions on what name you can use.
We know you've been calling for this change for a while. We know that our names policy has been unclear, and this has led to some unnecessarily difficult experiences for some of our users. For this we apologize, and we hope that today's change is a step toward making Google+ the welcoming and inclusive place that we want it to be. Thank you for expressing your opinions so passionately, and thanks for continuing to make Google+ the thoughtful community that it is.