Steenburgh, Thomas J., Jill Avery, and Naseem Ashraf Dahod. "HubSpot: Inbound Marketing and Web 2.0." Harvard Business School Case 509-049, May 2009. (Revised January 2011.) ...

Additionally, the company's target audience may be very niche, making it difficult to reach potential customers through mass marketing efforts. This is where inbound marketing comes in.

Steenburgh, Thomas J., and Jill Avery. "HubSpot: Inbound Marketing and Web 2.0 (TN)." Harvard Business School Teaching Note 510-043, September 2009.