In response to OP:
Call me overly-thorough, but I've found it's best to send that thank you email, or email to acknowledge receipt of information. With our rapidly-growing technological capabilities, I think we often forget about the impact that a simple thank-you note can have, especially on a prospective advisor or admissions staff person! When I'm wondering whether I should email a VIP, I always think, " would I rather Professor X think that I am overly-thorough and considerate in my communication style, or wonder whether I even received his/her email." I err on the former, and I think it's worked out pretty well for me.
In response to ElusiveMuse's question:
I spend a large part of my work days following up with and/or tracking down overly-busy faculty members and other professionals, as I am a research coordinator. I tend to email once, then if I get no response, I email again in a very nice tone, responding to my original email (so they can see that I've emailed twice now). WIth prospective faculty people, I'd leave it at that if they don't respond, or leave just one voicemail (some faculty are "old-fashioned" and don't really "do" email, so you might get a response this way). If still nothing, move on to someone else for your needs. That's just my standard operation procedure. Good luck!