You are perfect correct that Apple will know what music you possess. If that bothers you than iTunes Match isn't for you. Neither is the Genius Mix feature. And

You are perfect correct that Apple will know what music you possess. If that bothers you than iTunes Match isn't for you. Neither is the Genius Mix feature. And frankly neither is iTunes Store, Amazon shopping or the Internet (when you get right down to it). For me, I don't see actionable information from this. What is Apple going to do? Turn me over to the RIAA? Obviously not. At the very worst as far as I can guess, they could great a recommendation engine and try to upsell me more music that I might like. Sort of how a radio station works (inefficiently) or how a home town record store owner used to work ("Hey man did you check out Dylan's latest?") If they shove recommendations at me through email, ping or a "suggestions" feature in iTunes, I can ignore it. And it causes me less hassle than junk postal mail. Seriously, what can they do with it?