Disabling these 3 things will stop people from inviting you
An overview of the iChat preferences
Enable buddy icon animation
Stop people from seeing that you're idle (away from the computer and for how long)
Change the alerts and sounds that play
Change the default font you send IMs in
Enable iChat to auto respond to IMs
Enable your iChat conversation to be displayed in one window, like tabs in Safari
Change what iChat does when you use Fast User Switching
How to unblock someone you've blocked
Enable or disable iChat's menu bar icon, and change it's settings
