I have a problem which I have not encountered before. On a website I am working on, www.example.com, I have several affiliate links which are of the form www.example.com/out/blahblah

The redirect is a 302, as I have heard that 302 is the recommended redirect type for affiliate links.

The problem is that if i do a site:example.com inurl:out search, I can see the redirected urls show in serp, with the title and meta description of the targeted url.

I did not notice until today. And, as a curiosity I checked other big sites that i know have affiliate links and I noticed the same thing happens to some of them too. Some however do not have these links indexed and others have them indexed with the "this page is blocked by robots.txt" message because they probably have that.

example: see how yoast.com has /out/ blocked in robots , and it shows that message : https://www.google.com/search?q=site%3Ayoast.com+inurl%3Aout&rlz=1C1GIGM_enRO664RO664&oq=site%3Ayoast.com+inurl%3Aout&aqs=chrome.0.69i59j69i58.6783j0j4&sourceid=chrome&es_sm=93&ie=UTF-8

same for nuts and botls media : https://www.google.com/search?q=site:nutsandboltsmedia.com+inurl:go&rlz=1C1GIGM_enRO664RO664&biw=1920&bih=995&noj=1&filter=0

and check out carriedils.com which has exactly the problem I have : https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=site%3Acarriedils.com%20inurl%3Ago

What is the cause of this? Any recommendations?