You’ve heard of branding, but DE-branding?  In a world full of media hounds who’d kill to have their name in the spotlight, this seems almost implausible.  But indeed, last week beleaguered financier AIG decided to go incognito.  Their Water Street Manhattan office signage vanished overnight. Saying this was an attempt to differentiate this office-where much of the alleged financial shenanigans have taken place–from…