Career mentor specialists?

We live in an age of specialization. You see it in the medial profession, in corporate america, and in professional sports.  One area where I have not noticed a great deal of content about specialization is in career mentoring. Career mentoring itself gets a great deal of thought in books, blogs, and self-help publications. From my reading though, the act of career mentoring is regarded as a specialty (of sorts) unto itself. So I wonder, is it too much to try to have mentors in specific areas of your career?

For example, as an executive with responsibilities in multiple areas should you seek to have a mentor in each area? (Finance mentor, Strategy mentor, Information Technology mentor, Career guidance mentor, etc. ) The idea is to get more focused  mentoring with the trade-off of additional time commitment and complexity.

What are your thoughts and experiences with career mentoring? Have you used multiple mentors or just one?