Mad Props to Overthinkingit.com or as I'll call it "My New Favorite Website".
On the key changes of Livin' On a Prayer:
"If you bear the song as in minor throughout, it modulates E minor -> G minor, up a minor third. If you hear it as major, it goes G major -> Bb major, again up a minor third. If I understand Wrather right, he hears it as in minor before the modulation, and major afterwards, which would mean E minor -> Bb major, up a tritone (rad as hell!). And I suppose you could hear it as major before the modulation and minor after (G major -> G minor), but I find that reading a little perverse."
Read the rest HERE.