Organized tours - be careful. They all have single children/grandchildren. My parents used to ROUTINELY come back from cruises with email addresses of the children and grandchildren of people they had met, usually their dining companions. They were all "nice single young men." I never emailed any of them. And either my parents weren't giving out my email address, just letting me make the first move, or (more likely) the guys also chose to never email me because I never heard from any of them.

But this is a thing. Be wary.