Reicheld (1996)
Reicheld, F. The Loyalty Effect. Harvard Business School Press, 1996.
Includes discussion of the value of 'loyal' shareholders, as opposed to shorter-term traders. Some analysts, e.g., Livieratos and Balios (2004) argue that social investors are more likely to fit in the 'loyal' category, and that this could lower the firm's cost of capital by reducing volatility of equity returns.