In my experience designing ontologies for different groups, one 
  thing that I find keeps cropping up is that SMEs tend to create data 
  structures that most closely approximate their understanding of a subject, not 
  necessarily that provides the most optimal representation of that data 
  model.  
   
  My experience is complementary: I usually find that different 
  business people have 
  different perspectives on the information, and your job as data architect is 
  to moderate / facilitate dialogue / knock heads together.
   
  My first ever XML job was to design some application-interchange 
  messages for a cable TV company. Not seen by them as a data architecture job 
  let alone a business consultancy job; but within a couple of days I was 
  moderating an animated discussion between people from different divisions 
  of the company about whether or not their business plan included selling to 
  hotels or not. So: never assume that anyone you are talking to has the whole 
  picture.
   
  In this particular company the business people were much more inclined 
  to think in terms of business processes than information assets, so the 
  business process tended to be the starting point. But they were a lot more 
  interested in processes that were useful to the business, like installing new 
  customers, than into "grudge processes" like disconnecting ex-customers. When 
  you started discussing how things like that were supposed to work, they would 
  quickly lose interest and say "just make it happen".
   
  Michael Kay
  http://www.saxonica.com/