Right now, you can only Deauthorize All your 5 computers every single year. But why Apple can not deauthorize the iTune for ME, when OTHER people authorize it with their account? Technically it is very simple.
I sold 4 of 5 of my Mac computers in past 6 month, without knowing that I should deauthorize them before selling, and bought a new one. Now this 6th Mac computer can not authorize the iTune account. I have to wait for 6 month to Deauthorize all iTune accounts, then authorize the two I have. Is this what Apple is intended to happen? Or does Apple expect all the PC-convert-to-Mac consumers having full knowledge of this authorize/deauthorize policy before they convert?