[onreact-com]

OK, it obviously depends on which industry we actually speak of. The overall Web industry tends to do it wrong like in the example above. Creating two sites for the same content is fundamentally flawed.

From a SEO perspective we always try to avoid duplicate content issues and splitting up of your site authority. I'd recommend the current issue of the Search Marketing Standard Magazine (disclosure: I'm an affiliate of it) which features an interview with mobile SEO Cindy Krum. She explains the issue with separate sites/pages quite well.

On the other hand I have witnessed the negative impact of such subdomain based mobile SEO already years ago. It never quite worked with Google.

[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.