If you use an ampersand when posting data on the site (not through twitter), anything after the ampersand is stripped out. So 'ate pb&j' is recorded as 'ate pb'.
You can fix this by calling serialize() on the form instead of getting the message by using attr('value'). i.e. the line
data: "message=" + message,
could be changed to
data: $('form#action_add').serialize(),
The serialize() function will take care of escaping things like &s.
