Tag clouds generally have the following additional properties:
The words are arranged in a continuous list, rather than a table. The order of the words is uncorrelated to tag frequency; for example, they might be listed alphabetically or randomly.
The words represent tags, or community-created metadata. This metadata often follows power laws—there are few popular items, and many more unpopular items.
The tags are links navigable to the tagged content.
The first property gives tag clouds their cloudy or amorphous appearance. They have a simple beauty that is more attractive than a grid.
The second two properties give tag clouds a dual function. They function not only as a graph of interesting data, but are a navigation interface to user-generated content (or what Derek Powazek calls "authentic media"). In other words, tag clouds are both something to look at and something to click on.