Software that's just asking to be hacked.
I bought MacPaw Software's Clean My Mac today for my 2010 Mac Mini. This computer has three profiles (users): me as admin, and one each for my kids and my wife. I paid fair and square for one licence, because as far as I'm concerned, one licence = 1 computer, no matter how many different user-profiles are on it (I bet you can see where this is heading). I installed the software under me as admin (but making sure I selected the option which allowed all users to access it), including entering the licence code.
I ran the software and let it perform a scan and a cleanup. It worked fine, but I'm conscious that it probably only cleared-out 'my' rubbish and not that on the other profiles, because my profile can only access my files and the mutual shared area, not the private folders of other users.
So imagine my surprise when I asked my wife to run Clean My Mac under her profile, and the app gave her a message that it wasn't licenced to her so she couldn't use it without buying another licence. I tried entering my licence number: no joy, invalid licence number.
I can't tell you what I'm about to do next, because it's not big and it's not clever, but as far as I'm concerned, I've paid fair and square to use that software on that one computer, even if 500 people have different profiles on it, so my conscience is 100% clear.
Very naughty/sneaky, MacPaw software.
(Or maybe you have a more sympathetic view in their favour)