A few weeks ago during a fact-finding meeting with a prospective client (who became an SEM client shortly after meeting with the Enquiro Team and touring our offices) I was asked a very good PPC question.
The client-to-be asked "Other than branding, why would we consider running PPC ads on keywords we are already ranking #1 organically for?" By branding I assumed the client was referring to the 'multiplying effect' of having multiple listings on an SERP (Search Engine Results Page).
So why would an online company run PPC ads for keywords they rank #1 organically for? If there are no other ads on the SERPs they are ranking #1 for organically, they most likely would not. However, if the competition is advertising on those same SERPs, or the client has reason to suspect their organic listing will not do the job, PPC deserves careful consideration.