Does a Mac installation have an identifier I wanted to know if a Mac installation has an identifier with which apple could theoretically identify the machine? More concretely I am wondering if I clone an installation of for example snow leopard would the clone also have the same identifier, or does OS X not use identifiers like Windows does/did back in the day?

Thanks
As far as I can see it there are several ways to track a mac system:


Hardware-UUID
serialnumber
Mac addresses of network interfaces (and I think bluetooth as well)


The hardware-uuid seems to depend on the used hardware of the mac. It seems to change if one exchange e.g. a graphics card: 


  It is possible for a system to lose its serial number so that it
  will no longer appear either in System Profiler or the I/O Registry.
  Repairing a system by swapping hardware components is one reason this
  can happen. Apple does not document the specific details of how a
  machine can lose its serial number. Once the serial number has been
  lost there is no means to restore it to the machine.
  
  Apple does not guarantee that all future systems will have a software-readable serial number.
  
  Both of these cases illustrate why asset tracking software should always provide a way for a serial number to be entered manually.


Source

As far as I can tell they mean the UUID when they say „serial number“.

The serial number of the system seems to be fix. I have no prove for this other than that it is used for registering your mac with Apple.

Conclusion

In theory Apple as well as developers are able to identify your installation based on your hardware. If you clone your system to new hardware there will be new UUIDs and serial numbers for the new installation.