One is to get more real estate on the result page. Apparently, this helps get more clicks either on PPC or natural results when you have both an ad and a regular listing. Frankly, I don't know if that's true but if you have both, you double your chances of getting a click somehow.
Second, you can get factual data from your campaign. How many people did search for that term? PPC will tell you for sure.
Third, you can test different headlines and descriptions very easily and quickly. And again, having real data to fall on to improve your ads which could be used for SEO too.
Four, you can bid on keywords in PPC that you don't rank for in organics.
Maybe others can come up with more but these would be the biggest ones that I can think of. I do have a fifth one: in my experience, ads convert better than organics and usually get higher click rates.
When I have a term where the client's page is already ranking high in the organics, I'll often run PPC on the term but use an automated rule to keep the ad lower on the page.
I find that if the search contains the client's actual brand name, CTR is strong and the CPC goes down to the point that it costs us very little to run ads on brand name searches. I am not keen on outranking a strong organic listing with a paid ad, but if the clicks are cheap enough I don't worry about it.
I do find that both the ad and the organic listing get clicks, although it's not my experience that ads convert better. Sometimes yes, but sometimes no; it can go either way.
Thansk guys, great tips. Great responses and 5 or 6 solid answers we can take to the client. I also read somewhere that it's a different type of user that clicks on PPC as opposed to organic. Do you think there's any weight to this?