My digital booklet was corrupted and I was advised to update to the newest version of iTunes, which I didn't want to. So I went to Best Buy and signed into my iTunes account there, downloaded the booklet that was rightfully purchased by me, transferred it to my flash drive, and took it home. Success! However I think I forgot to sign out of the iTunes Store at Best Buy. When I came home, I found I have been signed out on my home computer (from iTS). I immediately signed back in.

My question is, should I be concerned? Will someone be able to use my account to buy music? Can multiple computers be signed into one account simultaneously?

ps. By the way if you are thinking about doing this, don't go to the Apple Store, because all of their Macs are signed in with a Demo iTunes Store account. Those computer won't let you sign in.