tagging is the fastest, purist form of graffiti. The point is to get you name up as much as possible with style in the hardest places as possible. You do this to get RESPECT. Respect from other writters, and other people that appreciate the art of graffiti.
your name says alot. it is who you are identified with. you get recognision from your name. your style also gets you alot of recognision. it is easy to tell how long someone has been writting by the style of thier tag. The more elaborate, the more respect.

names dont usually change during a writers "career". if the name is changed the writer gets less recognision because most dont konw that the writer has changed his/her name. numbers are sometimes added to names or other additions can be made to change the style of writting used in the tag.