With newaudiotechnology.com we eventually switched to using USB sticks as dongles.
The reason is that we noticed some paying users were cracking it, too, because our licensing system didn't allow dual boot or having a workstation and a laptop.
But our licenses were supposed to be per user and people wanted to carry our software around with them. If setup correctly, the same USB stick is now used both as licensing dongle and it also contains installers for Windows and Mac.
USB binding is fairly easy to bypass. Not script-kiddy level, granted, but it's still a matter of trampolining several API calls and then faking a presence of authorized USB device. At least on Windows.
The reason yours wasn't cracked is the lack of interest on skilled crackers' part.
Dongles don't prevent piracy. Famously, I remember paradox cracking several dongle-secured audio tools that were claimed to be "uncrackable". You may not even need to clone a dongle to do it.
The reason is that we noticed some paying users were cracking it, too, because our licensing system didn't allow dual boot or having a workstation and a laptop.
But our licenses were supposed to be per user and people wanted to carry our software around with them. If setup correctly, the same USB stick is now used both as licensing dongle and it also contains installers for Windows and Mac.