Except for the Galaxy Nexus, every single Android phone I have ever used has had a back button.
And, Ironically, The Galaxy Nexus is attempting to follow the iPhone model of using software. Thankfully it looks like developers are ignoring the Nexus and continuing to use hardware nav buttons.
Not even close to the iPhone. The nexus still has dedicated functional keys that disappear when watching videos only. The iPhone just has one big button underneath its 1 inch screen.
Google isn't following anyone. If anything theyre starting a new trend. A trend which every other android manufacturer will follow and apple too.