Not only cyber criminial but people around us that has an ill-intention. We never know whether people around us will change or not once they knew that we have lots of treasure in digital world. They maybe good to us but we all know how greed can change people. There are even cases where a member of the family killing their kin just to get the money by themselves. So it is really important that we keep vigilant and never expose that we are holding that huge amount of Bitcoin or else we might find ourselves in big trouble.
There is no doubt in this. Revealing your money to others is a grave mistake and every person whom you feel to be trustworthy can all of a sudden turn their morals against you and rob you. The internet is not the place to trust anybody and in real life your own money is at ever more stake. Hence the more you keep people in the dark the safer it is for you and your assets.
The person in front may have good intentions but they can flip any time in future and there is no way to know this if you are trusting them.