I'm one of the co-admins at Smiths Official All project which is huge. I had started Southern Smiths back in about 2002 and we merged in 3 major regional projects about a year and a half ago to include all Smiths/Schmidts/Smyths/Smythes of all geographical locations (http://www.smithsworlwide.org). Here are some reasons why people can't be reached, so there may be an erroneous perception they don't want to share. 1. The person doing the DNA test has not updated his or her email on the project. 2. The person doing the DNA test is not the person who is interested in the project but the other person's email is not there or has not been updated. 3. The person did the National Geographic test but isn't interested in surname genealogy 4. The person no longer does genealogy due to age, illness, or has passed away. 5. The person has spam filters set on but doesn't check regularly to make sure there aren't legitimate queries.
I know it can be frustrating. I used to have a *blind* emailer that emailed people directly, but have found over the now about 10 years of the project that if I do that, there's no way to know if the email even works anymore. So, what we do is put ourselves in the middle as intermediaries, try to email the person and if it bounces, we try sending a letter. Then we figure we have made every attempt we can on our end to help the participants communicate.