The number 8, 八!

EIGHT is a digit Chinese like to associate themselves with..
The word for "8" (八) in Chinese (pronounced as “ bā ”). It sounds similar to the word which means "prosperity" or "wealth" (发 - short for "发财", pronounced as: fā). In regional dialects the words for "eight" and "fortune" are also similar, eg Cantonese "baat" and "faat"..
Hence the fondness for this digit by the Chinese population world wide!
Coincidently, there is also a resemblance between two digits, "88", which represent the shuang xi ('double joy'), a popular decorative design composed of two stylized characters 喜 (xi, 'joy', 'happiness')..
So the more the merrier for this digit, be it in car license, handphone number, house number..

ps:
unfortunately, this year 2008, 8.8.2008 is not a consider an auspicious date as this day falls in the month of the "lunar 7th month" where the ghosts and spirits from another world is let out to "visit" this world..so..till another 8.8.8 strikes...again..