What is ARC and why do I need to know?

At the clothing fair and other big events the biggest enemy is LAG and ARC or Avatar Rendering Cost is one way we can help ourselves and those around us to reduce lag.

The SL Wiki states:
Avatar Rendering Cost shows a point score above each avatar's head which indicates how "laggy" they are on the viewer-side. ARC is found in Advanced Menu > Rendering > Info Displays > Avatar Rendering Cost. The score is a factor of the size and number of textures used, and the number and type of primatives used. Avatars with large textures, lots of flexi-prim parts and high prim count objects, and/or invisible parts will score higher than one that uses fewer/smaller textures, using a few sculpties instead of many basic primatives, etc.

For full explanation and breakdown of ARC points go to http://wiki.secondlife.com/wiki/ARC

The explanation is very clear and sets out what it costs for different attachments etc
While on the center sim while we were discussing how to let people know about this a lady appeared on the sim now Ihad my ARC turned on and was astounded when I saw a score of 132,862 over her head, well being me I grabbed a screenshot and then spoke to her.
Her name was Julia Tower, now Julia was aware of ARC and immediately removed a certain HUD she was wearing and her ARC plummeted to just 1820.
The next day i saw another lady with an ARC above 133000 and did the same again but this time she had never heard of ARC so i gave her the notecard and explained briefly. She removed a different HUD and her ARC dropped to less than 1000 she was stunned "That is amazing I can rezz everything now!"

Many people get upset about lag in secondlife little realising that they are causing it themselves but there is a flip side to knowing about ARC - in fact two:
People can get aggressive with those that ignore or dont realise their ARC
and having the ARC turned on also creates lag.
Informing people of ARC, in my opinion, can be a good thing but bullying or abusing someone because they have a high ARC is never acceptable all you should do is inform, after that it is up to the individual and if they ignore the advice then you can mute them to stop them from making you lag rather than create a scene or make someone else feel uncomfortable.
By all means reduce your own ARC and beware of certain HUDs which can ad over 130000ARC
if you are going to a big event then do what you can to reduce your ARC not only for your benefit but for everyone around you.
Thank you to Julia Tower for letting me use you as an example.
Dana Vanmoer