The question about affiliate links and google serps has been discussed several times but I can't find any discussion on our own situation.
Many pages on the site have an affiliate product search form, method = get. The affiliate site doesn't work with 'post' forms, so has to receive a 'get' type query.
Our site has been demoted by both panda and penguin and I understand from the affiliate company that many of their affiliates have experienced the same problem.
I understand that 'post' forms are never followed by google, so would it be a good idea to change these forms to be type 'post' to a page on our own site, blocked in robots.txt, that then redirects to the affiliate site as a 'get' type query...
...or is this seen as a sneaky redirect or cloaking or something else that might make matters worse?
IMHO simply having an affiliate link on a page will not cause penalties or ranking problems. I also feel that an affiliate form will generally not cause a problem.
What causes a problem is that many affiliates use identical content that is published on 100 other sites and develop very poor quality backlinks that are easy for Google to identify and devalue.
If you think that affiliate links or forms cause ranking problems, do a real test. Launch two test sites. One with the affiliate and one without and see if there is any ranking difference.
If you have a site that has been impacted by Panda and Penguin - you have bigger problems than having an affiliate form on your page. I think we can all agree that Penguin is basically about links to your site, which means the affiliate form is not a direct factor for your Penguin penalty.
I would take a step back and ask yourself how you can improve the value proposition of your website. How can you make the site content better. Great content & tools will help keep your remaining visitors, improve conversions and attract other websites to link to your great resource.