I realize after reading your post that I must also be misunderstanding something. I can use the same mobile app to log into different salesforce accounts regardless of which oAuth key I'm using (for example, I can successfully switch between Production and Sandbox).

I guess I'm missing what role the oAuth key plays here and would also appreciate some insight. Perhaps even just a pointer to documentation on this as I tried searching online and thru help docs but couldn't locate anything.

Hi:

I found an answer.  You are right, when you create a key,  Saleforce allows that key to be used on any organization.

My problem was that my oAuth was not using the different login URL required to log into my clients sandbox rather than into their production database. 

Joseph

Hmm, I guess I'm still confused on the role of the oAuth key. Does this mean it is only used to validate the app itself and therefore has nothing to do with the org being accessed or the user login credentials?

This had never crossed my mind before and I wasn't suffering from any confusion before reading this post so I wonder if I'm either misunderstanding the current situation or have forgotten something I had read when first getting going with Mobile SDK. I may have to start back at the beginning...

Chris