When is cloaking a good
The Bad Delivering content that is irrelevant to what you will show regular visitors is a violation at all search engines (spamming), and will get your pages dropped or your site banned, depending on how far off base you are. Delivering many pages that all lead to the same page is bad, bad, bad (spamming), you should optimize one keyword phrase per page, and make more pages if you want to optimize for another keyword phrase. If a single page contains many different topics, then consider isolating the more impotant topics on separate pages. This will also work for a shopping site, have less items per page so you can properly describe what the page contains. Delivering other peoples content is bad10 (yes to the power of 10), this is the most sure fire way to get into trouble. Except for the ugly stuff.
When is cloaking a bad thing? When you decide to bypass some limitations of search engine spiders and trick them in getting irrelevant content indexed.
The Ugly The only thing worse than delivering other people's content is to deceive a completely unsuspecting user into clicking on a link that leads to content which is completely inappropriate, and probably offensive based on the search keywords used and the SERP's returned. Everyone knows the examples so I won't mentioned them here. Flooding search engines with thousands of pages all leading to the same content is pretty ugly too.
When is cloaking an ugly thing? When you decide to bypass some limitations of search engine spiders and trick both them in getting irrelevant content indexed and people in arriving at sites the are offensive to them.
Depending on which of these tactics you have experience with or have been subjected to, you have likey formed an opinion of cloaking which is either good, bad, or ugly.
Which is it for you?