The only way to contact them is support@meetup.com and they only answer your questions when it's convenient for them. I am an organizer and have sent them several emails over the past month and I've received only 2 responses. The rest of the issues have not been address and I am still waiting on a reply.

support@meetup.com, and no I am not affiliated with meetup.com

I too have an extremely hard time connecting with headquarters. Once my meetup group became "one of the most active groups in the world", headquarters started contacting me. Still can't seem to get my pet peaves addressed directly though, so I'd say it's impossible.