I was looking through a few websites recently and noticed a trend I'm not sure I understand. Sites are creating unique referral URLs for customers in the form of:

http://customname.site.com

(If somebody were to use http://www.site.com/customname it would function the same way).

I can see the sites are using 302 redirects at some point using Google Chrome then doing some sort of htaccess redirect, taking the subdomain name (customname) and applying it as a referral parameter then keeping in session during the entire process.

However, there must be thousands of these custom URLs that people are typing in. How are each one of these "subdomains" not treated as separate URLs which in turn are redirected to the same page (in short, generating tons of links all pointing to the same page which Google would normally frown upon)? Additionally, the links also appear on the site themselves as clickable links so I'm not sure how these are not tracked.

Similarly, the "unique" url is not indexed or cached in any Google search results. How is this capability handled?

It does NOT highlight the referral aspect, but a true example of this is visiting http://sfgiants.com which does a 302 redirect to the much longer proper San Francisco Giants MLB homepage. I am wondering how SFgiants.com is not indexed (assuming that direct shortened link appears on several MLB pages)?

1 - I know these are 302 redirects, I can see this on the sites network flow.

2 - These links do in fact appear on the page itself because in some areas (for example, the bottom of the page may say: send this page to a friend! http://name.site.com/ which in turn would again redirect to something like http://www.site.com?id=name so the id value could be stored in session