The issue is that in a web browser, and Google Chrome is included, alternative PDF viewers can be used to view the PDF, which do not support the features in forms such as the Submit button. You can set Adobe Reader to be the default PDF viewer in Chrome, but you cannot assume other users have set it up that way...
We recommend against having users fill out a FormsCentral PDF in a web browser, rather offer the PDF for download to be saved and filled out with the Free Adobe Reader. FormsCentral PDF forms have to be filled out using Adobe Reader or Adobe Acrobat.
This FAQ explains more: http://forums.adobe.com/docs/DOC-4142