Google calls it sneaky redirects, and you may know it as cloaking. Of course, redirects are valuable, if employed legitimately to improve user experience.
Redirects are often used by webmasters to help forward visitors from one page to another. They are a normal part of how the web operates, and are very valuable when well used. However, some redirects are designed to manipulate or deceive search engines or to display different content to human users than to search engines. Our quality guidelines strictly forbid these kinds of redirects.Google Updates Its Guidelines For What it Calls "Sneaky Redirects" [googlewebmastercentral.blogspot.com]
To help webmasters better recognize problematic redirects, we have updated our quality guidelines for sneaky redirects with examples that illustrate redirect-related violations.
We have also updated the hacked content guidelines to include redirects on compromised websites. If you believe your site has been compromised, follow these instructions to identify the issues on your site and fix them.