And the biggest risk you run when cold-calling a researcher about his or her work is the possibility he or she will talk your ear off for far longer than you had planned for.

There are a few assholes that may be rude about being approached by someone outside their field, but I haven't met many of them.

Once, when I was a struggling grad student I was researching some topic in physics, I think it had something to do with exotic atoms... (For instance Positronium where an electron and positron orbit, or muonium where a muon replaces the electron orbiting a proton). I read a paper related to the topic and had a lot of questions on it, and really wanted to understand it better.. I recognized the name of one of the authors as someone that worked just upstairs in the physics department.

So, without finding out more about the professor first, I simply dropped by his office unannounced and asked him about the paper....

It was an incredible experience... he was friendly and I learned a huge amount, about far more than I had gone in there to ask him... he discussed his work with me for around an hour and a half...

In addition to learning the answers to my questions (and so much more) I learned that I had stumbled into the office of someone that had been an assistant to Schrodinger and Einstein, and had worked with Dirac.

Dr. Nándor Balázs wasn't just willing to speak with a lowly grad student, he was eager to share his thoughts until my brain was numb...