Hi Owen,
While it may seem that the identity management system for things is the same as for people (on an abstract) there are a few additional requirements IoT brings along. The most important aspect is that there are various limitations (in terms of code size, memory, bandwidth, battery life) of these devices. For that reason not all of the work that was suitable for a laptop/tablet/smart phone environment is also immediately applicable to the IoT environment.
If you want to read more about it have a look at two workshop reports:
Smart Object Workshop Report:
http://tools.ietf.org/html/rfc6574
Smart Object Security Workshop Report:
http://tools.ietf.org/html/draft-gilger-smart-object-security-workshop-01
(Smart Objects = Internet of Things)
Ciao
Hannes