I am mentoring a cousin and younger brothers of some of my friends who want to study CS or consider a career in this field. If they ask questions about how to prepare for a CS major, or eventually getting a job at companies, I tell them what I wish I had known when I was 17. I didn't have such a person to turn to when I was college age and was wondering whether this was the right career for me, given there are so many interesting options.
It only takes a few tens of minutes of my time to reply to their emails, but the type of mentorship, upbringing, or just sheer luck you had while growing up may not be available to someone else. Sometimes, it just takes a few words to help set their course.
While I am nowhere as accomplished as dmr, it's empowering to know that someone ten years younger would still love to be in my position, and that a few kind words can give them the encouragement to keep going.
Dennis Ritchie's death: 1,190,000 results from Google
Steve Job's death: 55,700,000 results from Google
Ripping off FreeBSD and Steve Wozniak's ideas are far more worthwhile than developing your own.
Another data point of an accomplished man being down to earth. I almost find this just a step beyond the call of duty.
Scenario: Imagine that you are looking for a job to the next hot small start-up. Send an email pretending that you are a high school student looking for a word of guidance. See if they will have the time to respond the same way dmr did. Judge