While it is true that anyone can reverse anything..... if it is hard enough, it reduces the number of people willing to try.
If you send an Eagle file to a fab, it includes the BOM, values, DigiKey part numbers, etc depending on how you configure your library. That makes it way easier than just seeing a bunch of pads on a board. I stopped printing part numbers and setup account with isolated and random emails.
Again, this only keeps out the casual counterfeiting. If someone wants my design, they will buy one to reverse - a leak from a fab house probably will not be a part of that.
Short and misplld from my mobile......