Difference between Google and Apple: Steve Jobs would commit seppuku before spending $5 billion on something he could remake, better, in a couple of months with a handful of dedicated engineers and a barn full of even more dedicated marketeers.
Isn't the difference just that Apple excels at marketing while Google sucks at it and know it ?
Google would be acquiring a great marketing team by buying GroupOn.
We'll see what Apple is going to spend its cash on, but it could be something that Google already has or could replicate easily but Apple can't generate on its own.
Compare the number of Android handsets selling versus iPhones. Compare the number of users of Ping and Last.FM. I'm not saying they're not good at what they do, or that they're not profitable at all.