Automated page generation
Automated page generation is sometimes a necessity, for instance, the pharmaceutical industry has to both provide information and protect information from misuse and ensure that information is only available to qualified doctors or surgeons.
However, some automated systems have been configured to generate more pages for a site in order to target specific keywords. WebPosition software is commonly used to generate door way pages. Doorway pages should be avoided as they are often created simply to induce a search engine to index the page - when a visitor arrives they may then either view the page - which typically has poor usability characteristics - and in most cases would backfire if the visitor is switched to another page - this is also known as cloaking.
Cloaking, or IP delivery is allowed for sites that need to determine user location - although in our experience there are other ways of achieving the same results. For instance one .com site we worked on had worldwide audiences who need to price in different countries. We did not want to redirect users for fear of receiving a spam penalty from search engines. We simply checked the time of the users machine and delivered pricing based on time differences, in Pounds, Euros or Dollars as appropriate - a simple solution to a complex problem.
There are of course situations where you have to cloak and to an extent these are tolerated, but again there are better ways. For instance this is where Yahoo's Paid inclusion program can work very well.
There are also needs to generate code to facilitate the technology of your visitor, for instance, you may need to test for different browser versions in order to ensure that on site services and features will work properly. The key is to avoid using these systems to changing text or raising HTML relevancy. This is a subjective area - best avoided.