If you stay within a local area network there is a big advantage to this, especially for live monitoring of manufacturing equipment and hospital patients. But when you go out into the Internet you have to worry about privacy invasion due to interception of the signals, having enough IP addresses to go around, and the cost of the data transfer as the bulk of the world pays for data by the MB - the more you put out or transfer, the higher the cost.

And that doesn't get into the security issues of someone hacking your M2M front door lock, etc or tracking your car or phone etc.