A Japanese programmer has created Footprints, a gadget for Google's Friend Connect service that aims to clue Website owners in to who's visiting their site and when.

Based on the Google-backed OpenSocial APIs, Friend Connect is an application that lets Website owners add social features, such as a profile button, to their sites by copying and pasting a few lines of code. Moreover, it's easy to use; users log in using an existing account from Google, Yahoo, AOL or OpenID.

The Footprints gadget for Google Friend Connect displays digital footprints for up to 10 site visitors, wrote Eiji Kitamura, a developer of one of the biggest portal sites in Japan, called "Goo," in a blog post. The gadget shows a visitor's name, photo, and the time that person last visited a site.

When users click on the visitor's photo it will take them to the visitor's profile, where users can learn more about and friend him or her. To keep users from crying foul over this gadget, an unabashed form of digital tracking, site visitors will be able to erase their footprints. Kitamura wrote:

I wanted to make this feature available for sites using Friend Connect because it is actually quite common in Japanese social networking services. It enables people to see who visited their diary (another popular feature) and encourages them to communicate with one another.

OK, but as we've seen from some of the things Facebook has tried to do (check out this latest Publisher imbroglio on ReadWriteWeb), by opening up user profile data to more users, Footprints may not get the same reception in the United States as it does in Japan.

Questions: Will site visitors have to erase their footprints for every Google Friend Connect site they visit, or is it a one-time opt-out? That's an important sticking point. Users won't want to rub out their digital footprints for every site they visit.

UPDATE: A Google spokesperson got back to me with this response:

You can delete your "footprint" each time you visit a website. If you don't want your "footprints" to ever appear on particular site, you can set your profile to be not visible to anyone on that website. To do this, sign in to the site using Friend Connect, click "Options," and then "Site settings." You should see sentence that says "Your profile is visible to anyone." If you click the hyperlink on anyone, you can change this to "no one." If you select this option, you won't appear in the Footprints gadget the next time you log in to the site.

Moreover, the Footprint gadget will only display recent visitors if they are signed in and have joined the site using Friend Connect, so if you don't join or sign in, you won't appear in the Footprints gadget.

It sounds like users have a reasonable degree of control when using the Footprints gadget. Would you use considering using Footprints for your site?