Re: Who's at fault?
Here's an idea that will probably get me nailed to a tree, but here goes anyway.
If you're a phone manufacturer and you decide to stop issuing updates (I'll be generous and limit that to security updates), then the last one you push should unlock the boot-loader (or make it available to download and apply to the phone via a cable connection if you're worried about the non-techie general public messing up their phones or complaining about some USP that you came up with no longer works).
I would quite happily live without all the bloat that some manufacturers insist on installing in favour of being able to easily apply stock Android or a custom ROM. Lets be honest, if your phone is older than 18 months then it's probably not going to be replaced "free" under contract or there's another reason why you haven't rushed out and bought the latest model, perhaps due to being burnt by built in obsolescence or not being prepared to spend a grand on a phone. Likewise you're probably not worried about that must have vendor specific hardware not working any more considering that many "features" that the manufacturers push are either duplicated by existing apps elsewhere or being handled perfectly well by the developer community.
Surely one way to beat the Android fragmentation issue is to encourage the manufacturers to allow their phones to become a vanilla Android phone if required once they determine it as having reached EOL. The consumer still enjoys the hardware they paid for without the guff that the manufacturer massaged into the cost at the point of sale and forced upon them for the life of the product. If the user wasn't going to buy a new phone anyway, what has the manufacturer lost by doing the right thing ?
Oh look, I managed to get all through that without banging on about Google moving the damn clo... oh.