Here’s an overview (my words) of what happened from MailChimp:
Due to the large size of our list, the http request to send the email timed out, resulting in no confirmation page being shown despite the fact that the email had been queued for sending. Subsequent attempts to send the mailing then caused the mailing to be queued again and again. MailChimp was able to manually stop the process during the 4th send. Their developers are currently patching their code so this will never happen again and improving the interface so that this is completely transparent to the end user.
Many of you are already aware that we have had a significant problem with our regular weekly user activity updates. These usually go out once a week, but in the last 48 hours the same email update went out to each recipient up to 4 times. Our sincerest apologies for the hassle this has caused many of you. We are working with MailChimp to identify the cause and make sure this does not happen again.
We will provide an update once we have identified the problem and fixed it. Thanks for your understanding and, again, we can’t say enough how sorry we are this happened!
The Blip.fm Team