Why Do Definitions - Why Not Just Use Wikipedia?

Today I spoke to the New York ERwin Modeling User Group (NYEMUG) on "Creating Great Definitions".  One question came up, which was why bother crafting definitions at all - why not simply rely on Wikipedia for them?  I suppose it could be any external source, and not necessarily Wikipedia (e.g. the Enterprise Data Management's Semantics Repository).  The way it would work conceptually would be to associate a link to Wikipedia with any term.

It might be thought that Wikipedia only deals with common terms, and not specialized technical terms.  However, there are a good number of technical terms that are present in Wikipedia.

My first reaction was both "yes" and "no".  "Yes" because it is simply obvious there is considerable value in Wikipedia, but "no" because Wikipedia does not understand the enterprise I work in, which ultimately supplies an enormous amount of context that influences definitions.   

I will have to think about this topic some more before I can fully answer it.  But, I at least wanted to capture a few initial ideas.  I take it for granted that Wikipedia has value, so I need to think why this value might be so limited that we still need to do definitions.   

(a) Wikipedia cannot provide details of a concept which is defined by a common relation of the instances included in the concept to another concept (usually a special way of managing these instances) that is unique to the enterprise (or part of the enterprise).  So Wikipedia cannot tell us what a Financial Asset is for our enterprise, because what we include in "Financial Asset" depends on our business model.    

(b) Wikipedia cannot deal with definitions modified on a per-context basis.  Speech communities are contexts.  So, for instance, Wikipedia cannot tell us what our Marketing department considers a Customer to be, versus what our Accounts Receivables department considers a Customer to be.  Wikipedia does not know the speech communities in our enterprise.

(c) The structure of Wikipedia entries differs on a per page basis.  There is no consistent set of sections to a definition, nor metadata for a definition.  This might inhibit use in an enterprise.

(d) Concepts are arranged in concept systems.  A definition shows how a concept is placed in a concept system.  One concept can occur in many concept systems, and the definition is modified in each case.

(e) Wikipedia can be wrong.  I have found errors, but very few - so I am not sure how valid this objection is.

Some of the above points may or may not overlap.  They are also preliminary, so subject to revision. 

That is all for now - I will have to return to this one.  However, the question raised in the title is one that must be answered.