http://www.quizyourprofile.com/guessyournumber.swf 

only two bits of information it needs in order to know the number you have picked is the first colour of your number and then the house that the number is in. the rest is just crap to make it look like its "magic".

if you pay attention to the numbers initially they are coloured in groups. when it gets to the house section they are different numbers that are coloured together. the initial grouped numbers are spread into each house so that once you select the house that your number is it knows the original colour that it was and then can tell the number you picked.

Correct!, mind you I only worked it out while on my way to the vinyards, gotta think of sumthn while I'm driving.