As was pointed out in our issue tracker:
http://code.google.com/p/mailchimp-api/issues/detail?id=38
campaignUnsubscribes() has not been returning the proper, documented
format since we launched it. That will be fixed tomorrow, 2011-03-09,
roughly around 12:00 EST.
Currently it is returning the email addresses as an array just like
previous versions (though in the "data" return parameter). A sample of
the current format in JSON is this:
a:2:{s:5:"total";d:1;s:4:"data";a:1:{i:0;s:19:"
a...@mailchimp.com";}}
The proper format that we will begin returning will look like this:
a:2:{s:5:"total";d:1;s:4:"data";a:1:{i:0;a:3:{s:5:"email";s:
19:"
je...@mailchimp.com";s:6:"reason";s:5:"OTHER";s:11:"reason_text";s:
9:"test test";}}}
So basically, where you were getting an array of strings, you will
start getting an array of array which contain strings.
To reiterate, this will *only* affect campaignUnsubscribes() in v1.3
of the API.