I've been trying to design a list with reasons why a proper theoretical physicist should understand the methods and the difficulty of doing experimental physics. So far I've only thought of two points:


Know how a theory can or cannot be verified;
Be able to read papers based on experimental data;


But that's pretty much what I can think of. Don't get me wrong, I think experimental physics is very hard to work on and I'm not trying to diminish it with my ridiculously short list. I truly can't think of any other reason. Can somebody help me? 

As a theorist, one likes to invent new ideas of how things might work. One crucial component to theory-building is searching the connection to experiments: A theory is physically meaningless when we cannot test it, for then it cannot be falsified. A theorist should be able to come up with experimental tests for his theories. This requires a good understanding of what experimentalists are (not) capable of. 

The perfect example here is Einstein (isn't he always?), who came up with a number of experimentally testable predictions of his theory of general relativity (those for special relativity were quite obvious, so he didn't have to work too hard on that). The most famous of these is the prediction of the correct deflection of light, confirmed by Eddington and a few others during a solar eclipse. 

A notoriously bad example in this aspect is string theory. It has thus far turned out impossible to come up with a way to test string theory, and this is regarded by many as a serious problem (although it may not have to do with the theorists' lack of understanding of experimental physics). 
