I think he was actually trying to piece together the background stories for the people who didn't respond to his emails, not find their emails. I don't think the info he was searching for was particularly private either.
For instance, trying to find out the company a CEO worked at before their current one. The problem is that content copiers will produce so many copies of the PR announcement for their current job, it's impossible to find the announcement for their previous job. I've tried doing this exact search and it's very frustrating.
I often find that things that really don't exist wind up with spam results. For instance, if you type in "free ipad" into google you will likely get thousands of search results, all spam because they don't actually exist.
Similarly, contact and personal information for CEOs of major corporations does not exist online either and any search will turn up spam.
One more example, to add to the many. If you get a genuine wrong number call from somebody who made a simple mistake and type their caller id into the internet, you'll just get a bunch of reverse phone lookup spam while if you search for a phone number of a know telemarketer or bill collector, you'll likely get a full dossier on that company.
For instance, trying to find out the company a CEO worked at before their current one. The problem is that content copiers will produce so many copies of the PR announcement for their current job, it's impossible to find the announcement for their previous job. I've tried doing this exact search and it's very frustrating.