To conclude this story, Google wanted a brittle back glass to sale more bumpers as well as (since glass is never warranted) sale a new phone to you or replacement part.
I'm sorry but thats the biggest load of nonsense I have heard. You'd have to try pretty hard to damage even toughened glass unless you throw your phone around alot so I fail to see how or why Google (or LG) would specifically engineer a phone to break unless you buy an extra part. And from what I've heard the bumper actually scratched the edges of the phone, just like the case for my current iPhone 4S does.
I've seen people drop glass covered phones (not always Gorilla glass) and there hasn't been a mark on them.
You are entitled to your opinion of course but to think a company would do that intentionally is a bit silly, in my opinion. Noone's compelling you to buy the bumper, there are probably lot's of other cases that will become available so you do not have to buy Google's bumper, so again I doubt they did it to force people to buy their bumper.
Phones are alot more fragile than older ones, NONE of them are made as solid as they once were. It's the risk you take with new age electronics.