I will thanks :),
Well I do have some domain knowledge, and many people in my surroundings who are real experts on this domain 
Bacteria and mold / mildew sensors would be great indeed. I have thought about them, this is however a subject where I don't have the relevant knowledge or expert network yet. Let's see if we can get some action on the agriculture use cases subject regarding this.
However this subject is not about a use case for agriculture but about more generic use cases in which having an RF-ID tag in the node might help. As the TTN Node is ideal for demo purposes I think there is definitely a use case for it.
I can imagine the following demo with regard to geoloation of sensors: The TTN infrastructure can provide coarse geolocation because of the GPS inside the gateway. Maybe when a sensor is received by multiple gateways the location of it can be determined more precisely?. The location of a node can be shown in an application as a circle on a map (maybe spanning severel square km/miles), now your (or my 
) smart app on our GPS enabled / RF-ID capable phone scans the RF-ID tag and suddenly the translucent location circle becomes a bright dot on the map 
Off course this is of limited value for mobile sensors (such as the TTN node), but as the node will be used for demo purposes the people who have the domain knowledge on stationary sensors immediately will see the added value of this RF-ID tag.
Offcourse this will put some demand on the "supply chain" / logistics of the TTN as the RF-ID tags and (default) node addresses need to be alligned somehow. (however for individual demo purposes this isn't stictly required).
As this is mainly a feature request for TTN node I will kick this subject to the Nodes category instead of Use cases. According to the timeline of the project, Q4 2015 is still used for finalizing designs so there is still a chance of getting it in I hope.
Maybe someone from @Tweetonig can give some feedback on this?