Identifying licenses / users from packed executables

[giv]

Yes.
A simple hash in the protected executable code could identify the user who own the legitimate product that protected the file.
Many vendors do that.
That is why some antivirus software alarm when a file is suposed to be protected with a legitimate protector.
The AV company have the watermarks for the real products and they don't recognise the cracked/patched etc. products.