It depends. Most famous people in tech aren't going to answer easily Googleable questions from a 20-year-old (or a 40 year old) But if you've got a genuine reason to be asking them, they respond more frequently than you'd think.

I wanted to use a purported quote from Maurice Wilkes that I couldn't track down a citation for in the introduction to my PhD thesis, so I emailed him. He must have been well into his eighties by that point. I got a very helpful reply and was able to use the quotation, properly cited (as well as add a "Wilkes, personal communication" to my citation list, which still makes me smile).