What is the meaning / advantage of a tag cloud ?
Is it a 'need to have' ?
If you're asking this question, definitely not. Wikipedia will supply you with a definition. Smashing Magazine has some examples, if you need some visuals.
They're a nice usability feature (as long as they're done properly) allowing for easier navigation, search and serendipity. You'll seen them on blogs and other content-heavy sites. So, it's definitely not a necessity nor is it appropriate with most sites.
By the sounds of it, you don't have a tagging system in place on your sites, so I wouldn't worry about it, if I were you. The tagging or "folksonomy" process has to be integrated into whatever CMS you're using.
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