[ig0rskee]

Well, it's pretty much a standard:

cnn.com & m.cnn.com

facebook.com & m.facebook.com

gmail.com & m.gmail.com

So definitely disagree with the notion of "fundamentally flawed" as literally every significant site is doing it at this point

[onreact-com]

Yeah, but do we need Gmail or Facebook crawled? No, both are private. They don't get indexed at all.

The CNN site is quite messed up. Check this:

"2 U.S. Marines killed in Afghanistan" site:cnn.com

You have duplicate content twice + the mobile version does not even contain the article when you click on the search snippet.