Cloaking - A Search Engine Optimizing technique?
I was thinking of doing some SEO (Search Engine Optimizing) stuff for my blog and I found this interesting method called ‘cloaking’ which many people might argue as a Search Engine Optimizing technique but I would say it is a search engine cheating technique 
For those of you who are wondering “what is Cloaking” and “what is SEO”; Search Engine Optimization is a process of improving the search engine related traffic to a site via search results for targeted keywords. Normally, the higher the rank of a site, its displayed in the top results of a related keyword search; which is why it attracts huge amount of traffic. Hence optimizing is important.
There are different ways of optmizing your site for search engines, by using relevant metadata on the webpages etc. Cloaking, many people consider, as one such techniques as well. But in reality its not a legitimate way of optimising.
What is Cloaking? Cloaking is a technique in which the content that is presented to the search engine spider is different to the content that is presented to the user. So a site’s web-master can create two types of content; one for the search engines and the other for the normal users (visitors). When a request for content hits the server, we can programmatically detect the requester and identify if it is a normal user or a search engine spider trying to crawl the site. This can be done from the User-Agent HTTP header. When its detected as a spider then the key-word rich content is returned. So the content presented to the normal users in this case is different.
Wikipedia terms cloaking as a black hat search engine optimization technique and I would call it a search engine cheating technique. Since the content returned to the spiders is keyword rich, the site would automatically get a higher rank and hence would be displayed in the first pages of the search results for the particular keyword.
Many Search engines have blacked out this technique and big search engines like Google ban such sites which use it and I think they should.
So best thing would be to follow the best and legitimate SEO techniques to increase the page rank and thus increase the traffic. If you think anyone is cloaking, then please do complain to the relevant search engine company to take an action and they should be able to verify and thus remove the site from the index.