I've often wondered about such "payment in the browser" options but... isn't this what we *do not* want?
Right now bitcoin payments happen quite easily. Just paste in the address, enter the amount, and click send. Done.
Wouldn't the "paypal" way require an intermediary website? Yet another site where you have to store your coins, will probably have to pay a fee, ...
Or you could go the route of browser extensions, but then only Firefox would benefit since Chrome's extensions are just javascript.
What we want is that bitcoin is adopted and used by the largest possible segment of the population.
Everything else is just cake.
Anonymity, decentralization, etc. are inherent to BTC and aren't going anywhere for those who appreciate those features.
But for everyone else, we should happily debase every possible aspect of BTC we can (except security, of course) in order to increase adoption to the largest degree possible.