Let's see what Eric Jordan has to say:
I won't state my opinion, I'll just quote Eric Jordan, and perhaps this will answer many of your questions.
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"When they view motion graphics, our audience becomes involved in the essence of our message. To enhance that, we should always try to connect with the viewer on an emotional level, to stimulate them through the use of carefully planned sights, sounds and motions.
An effective piece of animation will take into consideration how people respond to movements, tones and atmospheres. Quick-moving text and fleeting bursts of random light might stimulate energy or power, while slow-fading text and the relaxed unveiling of objects may indicate serenity or patience.
An effective piece of animation becomes a powerful form of communication, primarily because it has been given a soul by the designer.
The success of a flash site depends on how well we as designers use our innovative animation techniques to express the client's message.
Although clear communication is the goal of all motion graphics, the style in which we present them is unique to each of us, based on our own stylistic impressions.
This style will ultimately set the tone for the delivery. Balancing delivery issues with design aims was, for me, an important consideration as I built 2advanced.
Although I had no client brief to satisfy with the project, I had a message of my own to communicate.
Too many of today's flash intros use extraneous text just for the sake of having something to animate. To avoid this, I wanted to portray my message through graphics and carefully calculated movements. I focused on the speed and easing of my elements to give an overall sensation of awe and relaxed discovery.
Simplicity is a way of conveying calculation and awareness; a whisper can convey more emotion than a scream. I feel that it's the minimalist elements of 2advanced that strengthen its message and make the delivery more genuine. This is where my voice comes through in design.
One of the most difficult aspects of becoming fluent in the language of motion is finding a unique voice. I feel that I've found mine because I was lucky to solidify my style in the early stages of my design career. That has helped me to build a successful portfolio of well-branded projects."
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I suggest reading his section in Masters of Flash, you may find your answer there.