Go with a name. A couple of reasons. The first being that admin comes off as sorta corny (or at least I think so, others may disagree). A huge benefit is that you can keep the name as your online presence. For example, when starting a forum, we all know the value in posting in other forums to draw in members, etc. By keeping the same name, you become somewhat of a celebrity in your industry, and your site and name combo become your trademark. I'm known as "cscgal" on vbulletin.com, vbulletin.org, vbulletin.nl, theadminzone.com, sitepointforums.com, devshed.com, seochat.com, resource-zone.com, webmasterworld.com, among many others. When people see the cscgal name everywhere, they associate it with DaniWeb - just a little off-site branding ;)
It doesn't matter if you want to be ValueHosted, ShackBace, or Tone ... but whoever you are, be consistant everywhere. I got the name CSCGAL because it was my car's license plate. So when I needed an online username, I decided to just name myself after my car! Don't worry, it's a custom plate ;) It means Computer Science Gal :)
One Admin. This account is used to do official business. Warnings, mailers, site-specific issues (other then basic request/resposes), announcements, etc.
The other one is my name. It is used exclusively to chit chat, respond to threads, and etc. It is NEVER used to create an official response relating to the site, it's management.
a) It shelters my name id from harassment.
b) it allows me to transfer the Admin account temprorarily or permanently to an other individual. (I do like to vacation!)
c) Members recognize that when a response is from Admin, it is official, and not up for discussion, and is final.