I've setup a contribution page and made a link to it. I include a profile that includes things like address. The matching is set to update. If someone who already in civi goes to the donate page and only fills in the name and email address, leaving the street address blank, it will match and then null out the address that was there.
I'd like it to only update the fields if the user enters something in the field.
I don't really want to give everyone a drupal login and make them login first. We want to make donating as easy as possible.
We're using paypal so a lazy person who knows that and that they'll login to their paypal account and that it will pull up their address info, won't bother to enter it on the donate page. Interesting, if they do that either paypal doesn't send back the address info or civi doesn't do anything with it.
civicrm 4.5.8 (testing 4.6.11)