Your business plan is wrong...
Every business plan is wrong. The moment an entrepreneur hits "save" or "print" the plan is out of date. Things change. In some cases you grow ahead of plan (like portfolio company Jingle Networks whose 1-800-FREE411 service has captured 3% of the US Diirectory Assistance market in one year) and are faced with the challenges of successfully scaling to satisfy user demand. In other cases you find that some of your initial assumptions are no longer valid. A competitor emerges. New technologies emerge. You are unable to build a team as fast as you had planned. Distribution channel deals take longer than expected. Customer adoption is different than what you expected.
Either way - it is critical for an entrepreneur to be able to listen to the market, their team and their customers and make changes to their plan as necessary. I've always said that I'd much rather bet on an entrepreneur who can adapt to change rather than an entrepreneur who is convinced that they have the ability to predict the future. But adapting to change is hard. How do you maintain flexibility yet still preserve a goal oriented culture? What do you say to investors who backed your initial plan? When is a data point an outlier and when is it a warning bell? Munjal Shah, CEO/Founder of Riya is doing a wonderful job blogging about his experiences in transforming Riya.
(Disclosure: Riya is a portfolio company of First Round Capital).