Opinions requested on Cob designed walls?

I know that I shouldn't really put it here but putting it under the construction forum didn't generate much response.

I am designing the bones of my new garden bed and as a cheap alternative, I was thinking of making the walls of cob material. This would allow me to design a freeflowing wall much like hobbit villages. Has anyone used this method especially in z4 weather?

This is an example of cob construction:

http://www.1-sovetnik.com/Pictures/houses/Cob-houses/Page-1/cob-house-18-i.jpg
http://en.wikipedia.org/wiki/Cob_(building)
http://www.youtube.com/watch?v=2i1cHHJAguA