iTunes 10 allows you to hide your Ping sidebar, but not the drop-down menu for its "social network for music" that shows up next to every song you click. Here's how to kill that Ping button on Windows and Macs.
On a Windows system, Lifehacker reader sufreak suggests quitting out of iTunes, launching your Command Prompt (type "cmd" into your Start menu's search box), then entering the following command:
C:Program FilesiTunesiTunes.exe" /setPrefInt hide-ping-dropdown 1
If you're using a 64-bit Windows system, your iTunes might be installed in C:Program Files (x86) instead, so modify the front of that command to match.
On a Mac, the iThinkDifferent blog has your solution. Open a Terminal window, make sure you have your administrator password handy, and enter this command:
defaults write com.apple.iTunes hide-ping-dropdown -bool TRUE
Your days of mentally telling iTunes that you do not want to share how much you loved that second and third Queens of the Stone Age album, but not the fourth, are over.
How to Remove Ping Drop-Down on iTunes 10 (Mac Only) [iThinkDifferent]