the mac adress is the hardware adress of your device.
to keep your privacy it is good, to change your mac ( right on startup )

sudo apt-get install macchanger

or download at http://www.alobbs.com/macchanger/

download at http://www.klcconsulting.net/smac/
and follow the intaller instructions …

macchanger - MAC Changer

macchanger [options] device

macchanger is a Linux utility for viewing/manipulating the MAC address for network interfaces.

macchanger accepts the following options:

-h -v -e -a -A -r -l -m

-h, –help
Show summary of options.

-V, –version
Show version of program.

-e, –endding
Don’t change the vendor bytes.

-a, –another
Set random vendor MAC of the same kind.

-A
Set random vendor MAC of any kind.

-r, –random
Set fully random MAC.

-l, –list[=keyword]
Print known vendors (with keyword in the vendor’s description string)

-m, –mac XX:XX:XX:XX:XX:XX, –mac=XX:XX:XX:XX:XX:XX
Set the MAC XX:XX:XX:XX:XX:XX

write this in /etc/rc.local

iwconfig 2> /dev/null | egrep '^[a-z0-9]+' | cut -d' ' -f1 | xargs macchanger -r

macchanger is able to manipulate any given hardwareadress like: * wireless * ethernet * bluetooth * infrared * and more …