Originally made as a response to DominatingMommy's intro thread, this could be in admin stuff - but the ideal home would be as a thread in the hypothetical Newbies' Forum to give a little guidance to lurkers as to how to pick a good user name.
As to names... What's in a name? Well names like Raccoon, Moo, Peachy, Martin, while distinct on this forum, are common enough in the world at large that googling does not zoom the searcher straight to the user and his elsewhere details. This is a security feature. "Anonymous" is the ultimate example of this.
Kaishen or Babyjunior is the opposite to this; the name is distinct on the web and does lead to a person's website or other place they want you to go; they want the limelight. It is implied that they are confidant about their personal security on the web.
Incompletedude or Redtails or Eclipse deliberately suggests, accurately or not some aspect of personality, especially combined with an avi pic; Floydfan88 or Hata even more clearly suggests one of the user's interests.
PamPered18921 is typical of someone trying to be a bit anonymous but at the same time says that they self-identify with the fetishistic side of themselves, to the point it subsumes other sides of themself. This is not a hard and fast rule; some people with such a username are great members. But it is a red flag and people with such names tend to have an eye kept on them; they may be shied away from until they have established who they are through interaction.
"DominatingMommy" does suggest she emphasizes what the name suggests. This is only one side of her though, and I can assure everyone that she is fun to interact with on many topics outside of bdsm, such as strawberries. Nonetheless a name like this will be taken as an invitation to and by subby people, like Babyme would suggest the user is looking for caregivers.
Mentioning a detail like this says volumes about the person in a short space and is a very good intro-thread technique; other examples include I am a lifeguard, I have 4 boxes running linux, I am the CFO of a midcap-corporation, or I learned Norwegian so I could read Ibsen in the original.