MAC address change
 

I recently found a very useful option of the ifconfig command that lets me change my MAC address - hw for those who did not know. Now, the question is why; why can I change it? I mean, isn't that address supposed to be unique or something?

The address engrained in the HW itself is unique. It will be available again when the device is recognised by the system again if no modifications are performed. As for the reasons why I don't know, but given the fact that about everything is configurable in GNU/Linux, it's moot anyway?..

AFAIK some vendors (and others) use the MAC address to identify your machine. You might object to that...

Well, yes, its supposed to be unique and you will get into trouble if it isn't unique within a collision domain.

My guess is that shortly after the first person made the mistake of trying to filter net access by MAC address, someone came up with a hack to get around it, although it might also be the case that some of the supposedly unique-from-the-factory addresses weren't as unique as they should have been and a hack was needed to get around that.