ZydoSEO - 7:00 pm on Feb 8, 2013 (gmt 0) [edited by: ZydoSEO at 7:01 pm (utc) on Feb 8, 2013]
I have never seen any correlation at Google (or Microsoft/Bing) what so ever between buying ads and organic rankings. When we were spending $5 Million per month on PPC there were no increases in rankings. When we went dark for 6 months on PPC (from several million $$$ per month down to zero) due to the economy, we saw zero adverse effects to organic rankings. If spending millions per month on AdWord doesn't get you preferential organic rankings, I don't know how spending "only a small amount" each month would help you organically.
Yahoo! was a totally different story back in the day... Their old SSP (Search Submit Program) program where you could essentially specify a few site links that you wanted added to your organic listings and you paid per click when people clicked on those organic site links DID affect organic rankings. We used SSP for years and were ranking #1 on Yahoo! for very competitive terms (e.g. mortgage, refinance, home loans, etc.) the entire time. In Spring of '09 we let the SSP contract expire. The DAY it expired organic rankings for those phrases dropped to the 2nd page on Yahoo! 3 months later we renewed the contract. The DAY the contract was effective, we jumped right back to #1 for those keyword phrases. Of course, Bing chose not to implement SSP when they completely took over powering Yahoo! search, so SSP was retired.
[edited by: ZydoSEO at 7:01 pm (utc) on Feb 8, 2013]