If you need to get going quickly to ride the wave of a fad before it fizzles, then fast, bare_bones planning may be all you've got time to execute. This works best when you've already got the infrastructure in place, perhaps from previous projects or an established business, and you can simply shift energy and resources to the new idea.
Having a business plan is so important to you as an online marketer. But most people, who start online businesses, especially small businesses, do not really take the initiative to make a business plan. Probably they think that it's not necessary. But for sure there is little you can achieve in life without proper planning. More so in the contemporary times when survival depends largely on one's ability to organize your physical and mental resources well. The future is actually for those who are organized. And the future of your business is dependent on your good planning.