Hmm. What if Apple streamed music through Facebook (with integrated social features ie Ping) as a premium service and split the revenue with Facebook. Facebook's install base is so large, cost-leadership wouldn't be necessary to beat Spotify etc.

Also, I could see some teamwork between their respective game platforms/businesses. Buy an App Store game, you get to share it with two of your Facebook friends (send them a download token), which creates many more word of mouth sales, etc. Just seems Apple are the people poised to actually capitalize on a massive social network user base.