After an hour or so of going through the code to figure out why my petition wasn't working I spotted this:

// search to see if this was an existing contact. by default, we only
// based on email. @todo someday, this should be user configurable.

Until "someday" comes :), would it be possible to add something like:

8. Be sure that you have an email field on your petition form.

to the INSTALL.txt under the INSTALLATION section.

Thanks!
Scott