Meetup.com has had a series of bad days. Their site has been under a distributed denial of service (DDOS) attack for a number of days. To mitigate the problem, they are using the CloudFlare service, but even that has not been working great.
The net effect is that sometimes the Meetup.com site is unavailable, making it hard to sign up or schedule or reschedule events. The Meetup periodic announcements about the problem emphasize how hard they are working to fix it and how user credit cards are not at risk.
I've been happily using Meetup to organize the A2B3 weekly Thursday lunch series that I run, as well as a monthly Ann Arbor civic technology meetup and a monthly Web Analtyics Wednesday meetup. Of the three, only the a2civictech group doesn't really have any other infrastructure; the other two have existing web sites or mailing lists to carry on even if meetup is down.
Meetup is still under a DDoS attack. All data secure. YOU CAN COUNT ON MEETUP to be stable and reliable soon. http://t.co/YyNXdsq9b5— Meetup (@Meetup) March 3, 2014