There are multiple methods of getting to your target audience, and of course some methods are more efficient than others. Focusing on just one channel is very precarious strategy.
Scenario:You have a website, you have a very strong online presence with a client base stemming from Natural Search Engine results from Bing, and Yahoo, Google, Not so much.
One day the algorithm for the search engines change, and your SERP (Search Engine Results Page) Disappears, overnight.
This happens, all the time, every day!
Management did not allocate a budget towards other channels of marketing, and once that well dried up, now management is in Reactionary Mode.
Pay Per Click Marketing
Utilizing PPC marketing, you are guaranteed to get results, SEO cannot offer that. The only time you are billed is when someone clicks your ad. Pay Per Click Marketing within the Google, Bing, and Yahoo networks can help you more towards a successful campaign.
With Pay Per Click Marketing, management allocates a budget towards the auction for page placement. Page placement being where your ad appears in the Search Engines/network. SEM (Pay per Click Marketing) comes in varied forms, each having their strong points.
Anyone versed in business can tell you there is a cost for every action made, and that includes to actions not performed. It all comes down to being Proactive vs Reactive, relying on just one channel for your conversions can be costly, if management decided to be proactive and diversify their channels their is a cost too. One of the potential dangers could be if that ONE channel dries up, Then a steep price tends to be paid.