Real Life name being Neil Kimber. Grew up in Purley, UK. Am slowly experimenting with this Wikipedia thing. And a very fine thing it is too. I now live in Atlanta in the US and long for home.
Dbnull is a technical 'Type' in the Microsoft .Net CLR. It represents a null value returned from a database using ADO.Net.
It's a subtle joke to techhies as it implies that the actual database entry for this user is null. It also implies that the Wikipedia website is running under .Net, which is unlikely in the extreme.