We just discovered that there was a bug introduced to webflow.js on Monday morning (04/14/2014 12:15am PST) that caused Text Area form field data to not be sent to Webflow servers. This bug was fixed at on Tuesday afternoon (04/15/2014 4:15pm PST).
IMPORTANT: If you have a site that has a Text Area field, and you published or exported it during the time the bug was live, please republish your site to include the latest version of webflow.js - this will make sure that Text Area fields work properly.
Note: If your form was set to a custom action, or is configured to send data to Mailchimp, it was not affected by this bug.
Please accept our apologies for letting this bug out into the wild. To make sure this never happens again, we're working on creating some end-to-end tests which will run after every code deploy and verify that every type of form element (including the recently introduced checkbox and radio button fields) is capturing data properly.
P.S. Hat tip to @rowan for helping us troubleshoot and fix this issue.