"Reasonable Belief" is whatever you think that it is. You need to articulate what your standards are for "Reasonable Belief" in your CIP policy. The regulation itself was purposely written to leave that standard open for each institution to set for itself.
Does this mean that you won't be second guessed by an examiner? Probably not, since any self-set standard is open for criticism. IMHO, this will be a constantly evolving area, and I would guess at some point down the road, you will find a general consensus as to what constitutes "Reasonable Belief."
Also, I think the standard will be different for large regional banks vs. small, community-based institutions. For instance, if you have an officer that serves on the same YMCA/March of Dimes/local Chamber board as a promenient business customer, then I would say your "Reasonable Belief" is more substantial than someone who is never seen in our outside of the bank.
_________________________
CRCM,CAMS
Regulations are a poor substitute for ethics.
Just sayin'