When it comes to search engine optimization, the importance of having a strategy cannot be denied. The strategy within the strategy is to get results, but without a specific SEO marketing plan you're left with no specific course of action to improve your search engine rankings.
Search engine optimization has much of its roots in advertising and marketing, and thus shares similar planning requirements. In marketing one would never spend thousands of dollars on a campaign without a clear vision of how all the elements of the campaign will fit together. The same goes for SEO. One should only invest in SEO if it is created with a specific strategic plan in mind.