Sometime the shortest responses are the best. A Google Webmaster Help thread has a long detailed example given by a webmaster looking to do some cloaking to make their site work.
He goes through this long walk through of how the web site will function, what the URLs may look like, what content a user might see on one URL and what the search engine spider might see on an another URL. But he explains the content will be the same but the URLs will differ.
The only thing different in pages that robots and visitors end up on is page URL, not page content (aside from rel="canonical" at the main domain).
Should he do it?
John Mueller at Google said, basically, no. In a very short respond, John wrote:
Giving mixed signals like this is not going to deliver consistent results over time. I'd strongly recommend finding one site structure and using it consistently.
Check out the thread, what do you think he should do?
Forum discussion at Google Webmaster Help.