Android :: Stable Contact Identity

In the course of moving to the 2.0 cotnact APIs,"As long as the contact's row ID remains the same, this URI is equivalent to CONTENT_URI. If the contact's row ID changes as a result of a sync or aggregation, this URI will look up the contact using indirect information " Currently, we store contact IDs to identify particular contacts. If I read this right, contact IDs will no longer be stable in the world of 2.0, and we will need to store a lookup URI (or at least a LOOKUP_KEY and a row ID) in order to identify a contact in a stable way.
That would be a substantial change in our code. So, before I rush off to do it, I'd love to find out if a contact row ID change is going to be a routine thing (say, on every sync), or if it will be a very rare thing (say, when two contacts are manually combined into one, or some even rarer exception).