I am always amazed at how incredibly smart people can be seemingly unable to connect freaking dots.
Sorry, tptacek, but this is 100% related. If you, or anyone on HN, is concerned about ISPs being able to sniff the intent/payload of your traffic, then you're fucking stupid.
Why? Because the NSA has been doing it for YEARS. Here is a MAIN STREAM story on their institutionalizing of this activity in Utah which is NO SECRET!
It doesnt even matter "how ISPs actually identify file sharing traffic" -- it is TOO late.
File sharing is a ruse, a red herring, who the fuck cares about file sharing. This is about TIA (total information awareness) they don't care if you file share!
They use file sharing and copyright to enact laws that make binary wiretap both trivial and legal.
They want to know EVERYTHING you do - and by claiming you are a criminal via file sharing, they can install stupid ass gateways in the last mile, which just makes it seem like they follow some due process - there is NO LAST MILE. THey have every single bit, already!
They have already compromised the ISP, this is just a scare tactic to keep out the fluff. The fluff are those would would think that their stupid file sharing is alerting the feds, such that they refrain from doing so.
So, in closing, what the NSA is doing, on mass scale, is FAR more pertinent than what you would think.