Within your Social Profile settings, there is a 'Privacy Setting' which allows the user to set their social profile to either Public or Private.
If Public is used, the user is giving permission to display his/her contact information including First and Last Name. If Private is used, all of this information will be hidden except Alias, Title and the user's About Me section. Private accounts will not appear in the People tab and all posts shared will be made under the user's alias.
To change this setting, login to the portal. On the top-right of the page, click on your name and then click My Profile.
On the resulting page, click the Edit Profile button and you will see the Edit Profile menu. Under the Privacy Setting selection box, choose your privacy setting and then click Save Changes.
For more information about Social Profiles, see the Help Documentation.