The problem with this argument is that you don't need to be the NSA to compromise an unauthenticated encrypted channel; that's a task well within the capabilities of online criminals.
I'm didn't mean NSA specifically; that was just an example. I know it doesn't require massive hardware or anything like that because it doesn't involve breaking the encryption.
My original point is twofold:
First, having encrypted/unauthenticated communication is still better because it takes more effort to intercept, while doing so for unencrypted/unauthenticated is trivial (e.g. Google's WiFi sniffing debacle).
Second, encrypted/unauthenticated can be implemented to be almost completely transparent (for example, server and browser do a key exchange on every request; kind of how gzip compression is automatic), whereas encrypted/authenticated requires certificates (which you have to pay for, renew, copy on your server, etc.).
Right now X% of sites use HTTPS and (100 - X)% don't. It would be best if 100% of sites used HTTPS. But using _some_ form of encryption for the (100 - X)% is better than nothing, and more achievable than saying "encryption-only is useless, everyone should use authentication as well".
(I can't find any stats for HTTPS usage, hence the variables.)
