I'd like to add another perspective....I am a government employee (RN) in a state agency. My phone rings all day long with high school and college students essentially wanting me to do their research for them on a wide range of topics (having nothing to do with my role with the agency). I am amazed at how little prep they do before they call or drop me an e-mail....and they have extremely exacting expectations (I want 1500 words from you, I need it by tomorrow, etc.).
On a related topic, because I have an unusual job, I often speak to nursing school classes about my job. It is an interesting job and has great hours, weekends and holidays off, etc. I get a million requests for "how can I get a job like that?" ...I explain the process for state employment, that it is competitive, but that I'll walk anyone who is interested through it and help in any way I can. Of the 30 or 40 people who have shown enough interest to follow up, not one can get beyond the fact that a panel interview is required...they all say the same thing "hey, I'm a nurse, they should be lucky to get me!".
I agree with fab4fan and llg and smilingblueyes, if people are upfront, then you can respond or not, as you wish.