There is at least one important user-experience feature provided specifically by wrapping inputs inside a form tag:

The enter key will submit the form. In fact, in Mobile Safari, this is how you get the Go button to appear on the keyboard.

Without a form wrapping the inputs, there is nothing to submit.

You can of course provide enter-key behavior through a keypress event, but I don't know about if this works for mobile devices. I don't know about you, but I'd rather work with the semantics provided by the browser than have to imitate them with events.

In your case, you would simply provide an onsubmit event handler for the form, which would do your AJAX submit, then return false, canceling the actual submit.

You can simply provide action= (which means self), and method is not required — it defaults to GET.