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.