How to remove ping from itunes (Version10)
Enter the iTunes preferences, go to Parental, disable the Store. Ping goes (and so does the store).
If you want to access the store in the future then you can by re-enabling it.
Apple, if you are listening, why oh why do you add something to the sidebar without a way of removing it? For people who don't want Ping all you have done is force the stuff they do use (playlists) further down the page.
As UI specialists, you really should know better!!!
as a bonus, not having the store visible means you won't have the temptation to buy stuff you don't need. If enough people disable the store, maybe, just maybe, Apple will give a checkbox to remove ping (just like they do for radio, podcasts, tv etc).
Hope this helps others.