What is ‘the dark side of business relationships’ and what are the causes of its development?

question：
A) What is ‘the dark side of business relationships’ and what are the causes of its development?
B) What are the possible measures to manage the ‘dark side’ and how effective are they likely to be?
Answer the two questions separately, each for about 400-500 words.
References:
• Villena, V., Revilla, E., & Choi, T. 2011. The dark side of buyer–supplier relationships: A social capital perspective. Journal of Operations Management, 29(6): 561-576. • Anderson, E., & Jap. S. D. 2005. The dark side of close relationships. Sloan Management Review, 46(3): 75-82. • D. Ford, L.-E. Gadde, H. Hakansson, I. Snehota, Managing Business Relationships, John Wiley