Saxat från forzamotorsport.net:
"Q: I received the following message while trying to access a feature in the game "Your gamertag has been banned from this feature. For more information about Xbox LIVE's terms and services agreement, please visit Forzamotorsport.net". What did I do wrong?
A: If you have received this message then you have been banned from a specific feature on Xbox LIVE. This can happen if you upload offensive materials to the Storefront/Auction House, or use exploits and cheats to better your lap times. If it is your first time ban it will most likely be temporary, however depending on your offence we reserve the right to permanently ban you from a given feature. The duration of your ban will be displayed in a message sent to your Forza Motorsport 3 “Message Center” which can be found by navigating to the “My Profile” section of the Forza 3 main menu.
Currently we are banning users who have created an item that contains any of the following elements:
Depictions of nudity and/or sexual themes and suggestions. This includes “censored” designs or items that are deemed inappropriate.
Depictions of racism, hate crimes, bigotry, and discrimination. This includes any references to the Nazi regime.
Depictions of drugs and/or narcotics.
Fraudulent depictions used to trick players into purchasing your item.
Derogatory comments or remarks targeted at another user, person, or group.
Offensive language and profanity.
Any political references that we deem as inappropriate or offensive.
Additionally we are banning users who post cars that offer Microsoft Points (via hidden layers and codes), as well as users who are selling Forza Motorsport 3 credits on eBay. If you auction is not appropriate for all ages then you should take active steps to remove these design elements to avoid getting banned.