A friend of mine was tempted to read the private online chat conversation of her boyfriend. Her reasoning for this digression was that she was on the verge of taking a major relationship decision. She felt it was right to have as much information as possible before she takes a giant leap involving her to quit her job and relocating to a different city.
It was not a question of trust but cold feet. All she wanted was a few more assurances and signs to make her mentally ready for this transition. However in the search for the reassurance she ended up prying into documents she was not supposed to read. She rationalized it by giving a zillion reasons and examples of sharing between couples etc. Further she argued that a lot of people hire Private Investigators who also often breach the privacy and it is socially acceptable (although considered paranoid) to do so.
However there are faults in this theory. Since all these conversations were not intended for her, there is a strong likelihood that she could misinterpret them or be out of contexts. Most human beings esp. men are quite complicated and often tend to hide their true emotions. Sometimes this is because what the society expects them to do but also sometimes because genetically a guy is a social moron.
However the question still remains. How does one resist the temptation of going through the stuff that you know is important, is valuable to you yet you should not read. How does one draw a line between honoring the personal privacy of someone you love and satisfying ones curiosity.