Also, what's the point of having a "carefully guarded TLS connections on the Internet", if at least one of the ends is completely compromised?
Prefect forward secrecy is a lot more secure since if google's private key were compromised any traffic -- including traffic captured in the past -- would still be secure (baring some further compromise).
Each connection has 2 possibly transient negotiated public/private key pairs made just for that connection. In theory, google could store all these pairs as well and they could be compromised, but that adds up to a lot more ifs.
As near as I can tell, the extra computation required to do perfect forward secrecy is a large part of why its not more frequently implemented.
If you think Google is the only company that can secure webmail, I bet you are an employee.
But anyways: what does it matter if your webmail provider isn't beholden to the government, if a suitably motivated teenager can read your mail because of software vulnerabilities?
Google Mail isn't likely to be more secure just because Google is inherently better at building software than anyone else. Rather, it's because they allocate more resources to the problem of keeping Google Mail secure than any other mail provider does (or even can) allocate to their security.
Second, the equivalence isn't false. The Venn diagram of sites that can be compromised by script kiddies is entirely contained by that of sites that can be compromised by NSA.
Please do tell which one? And why you are sure they are not beholden to a government?
Only if that single feature outweighs your other reasons for switching away from Chrome.