The e_marketing plan is built exactly on the same principles as the classical plan. There is no different approach, but there might be some formal differences given by the uniqueness of the internet environment. Many of these differences come from the necessity to ensure a high rate of responsiveness from the customers, since the e_world is moving faster and requires faster reaction from its companies, compared to the traditional offline marketplace.
When I ask entrepreneurs and small business owners, it is not unusual for not having any marketing plan. I once read that Sir Richard Branson never had any marketing plan when he started the 1st Virgin business many years ago. In fact in one study of entrepreneurship (I couldn't recall the name of the study) was that as much as 50% of entrepreneurs and business owners don't have a business plan and marketing plan when they first started the business.