Send a follow up email after an event that includes links to profiles for all of the people that attended the event. Suggest a follow up..
As a meeting attendee, I would like to get an email notification a couple of days after my event to remind me a) who was there (Yes's/Maybes) and b) suggest that I follow up with them. "Did you enjoy the xxx event? Below are the attendees. Consider sending a follow up message that says "yyy". Where yyy would rotate and say "Nice to meet you", or "Would you be interested in having lunch?" or "I really enjoyed what you had to say about that one topic".
The "Consider sending..." language might be useful -- might not. Also not clear from my original post -- you would definitely need to display linked profile pictures in the email too.