I'm not entirely sure, but I believe the content/action script, needs the name of the submit-button to decide what action he will perform.
You can solve it like this:
-start from your working example
-hide the submit button with a touch of css (display:none) -Make a link (with javascript) that will click your submit-button.
I saw you found a solution, but to answer to your initial question:
everytime you have a from that perform an action that change the state of your system (add delete or modify), the W3C ask to use a post action (not a get, ie. not a link). This avoids, for instance, robots of the search engines creating zillions of drafts while indexing your site.