Audience

For the General public:
Give/show details
Give/show accuracy
Show how it applies to the real world
Provide an appearance of realism
Simplify complex ideas or processes
Provide 3d or 4d representation of non-spatial data
Provide historical background
Make result to that it can be quickly interpreted
Associate sound with visualization
Provide voiceover
Use predetermined (cultural) conventions (red=danger)
Indicate relationship between visualization and knowledge
Use "common" knowledge and historical icons

For Sponsors:
Dazzle them
Peak their interest
Encourage their return
Show the importance of the work
Show payoff of the work
Tacitly communicate information too complex for direct communication
Sell the product
Make it easy to understand
Project technology forward into the future
Demonstrate grasp of topic
Stay employed
Project feasibility
Explain limitations

For Ourselves:
Glean general conclusions from visualizations quickly
Build it and have it result in an educational tool
Transmit & receive large amounts of data
Relate science to general perceptions
Extract essence of data into knowledge
Clarify topic or determine patterns for interpreting data