This is a loaded phrase. It presumes that there exists either resources, manpower or knowledge which can and perhaps should be "tapped". It also is an assumption that such are ready and available, if those who have the ability and position to "tap" them would just do so. Included in the phrase is the implication of a waste existing, or an advantage not employed. 

Potential can also be applied to methods. How many times has the phrase "have you tried ..." been the response of one to whom you have gone for an answer or assistance. While in many cases you may have already "tried ...", there are times when such a hint is all you need in resolving the difficulty or challenge you are facing. It was there all the time (potential) and had only to be "discovered". This is the nature of most of the "UntappedPotential" that exists. If it were known to be available or a possibility, implementors would have "tapped" it and exercised its potential. 

It is important then that one be ever on the look out for potentials and opportunities for success to be discovered and "tapped".
-- DonaldNoyes
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