questions

where does the difference in usage come from? growing up in the usa, i never questioned using a . to designate the decimal point or a , to separate thousands from hundreds. so is it just another difference between the usa and the entire rest of the world?

commas for thousands are english measurement.

the periods for thousands are metric.

1,000.00 : enlish
1.000,00 : metric

http://en.wikipedia.org/wiki/File:DecimalSeparator.svg

With China and India on your side, i think the dot wins :)