At the f8 developer conference that Facebook held last week, Mark Zuckerberg announced that, along with launching its new Like button and the Open Graph API, the company would also be working more closely with a select group of outside partners on “instant personalization” integrations that will tie Facebook into the core of their sites.

The announcement led to people worrying about the privacy implications, and most recently some attention from certain US senators.

So, to illustrate how the service works in practice, we’ve put together a review of the instant personalization implementations for Facebook’s first three partner sites: Yelp, Pandora and Microsoft’s Docs.com.

But first, a bit more about what the instant personalization service is.

Facebook shares general information with certain partners of its choosing. This includes “your and your friends’ names, profile pictures, gender, connections, and any content shared using the Everyone privacy setting,” as well as some location data, according to the company’s new privacy policy.

The service requires each partner site to display a prominent blue scroll-down bar allowing users to instantly opt-out. If users don’t choose to opt out, the partner continues to be able to access general information. The exact terms of what sites are able to access is worked out between Facebook and each site, according to the company’s newly-implemented terms of service.

The point of instant personalization is to cut out a step for the user, thereby making the user more likely to use Facebook on the site. If the user is already signed into Facebook, the above sites can call on their profile details through the Facebook cookie in their browser. Other sites, like those that use its social plugins, also require users to be signed in to Facebook. Users can disable instant personalization in their privacy settings on Facebook if they don’t like the experience itself.

People ahve a wide variety of views on what’s acceptable for Facebook to do in this sort of interface. Some would prefer the personalization service be opt-in, for example, not opt-out, as certain US senators said this morning. Here’s our look at each integration. Readers can decide for themselves whether or not the service is invasive.

Yelp

During his part of the f8 keynote, Mark Zuckerberg used Yelp as his primary example for personalization. It served the purpose well, because Yelp has an obvious real-world relevance with its business and location reviews that Facebook has not totally captured yet (allowing location-based startups like Foursquare and MyTown to step in).

Yelp, in return for the assistance, has made its Facebook integration front-and-center. After you’ve gotten rid of the blue welcome bar at the  top, Yelp retains a small-font line in the same place noting that it’s using Facebook for personalization, with an options button that lets users instantly opt out or get an explanation of what is going on. Beside it is a friend activity button to show recent reviews from Facebook friends. At the bottom, a gray bar pops up showing which friends are already on the site.

Also on the front page, the top of the right side bar displays the names and profile pictures of your friends who are also on Yelp. Interestingly, this sidebar box and the rest of the Facebook apparatus disappeared once I logged in with my Yelp username, even once I’d gone to settings to log back in with my Facebook profile; Yelp appears to be struggling a bit with graceful integration of the two different profiles.

There’s a little more within business reviews. Right beneath the business name is one of Facebook’s “Like” buttons, which can publish back to your feed. And right above the review stream, an option to see Facebook Friends’ reviews has appeared, allowing you to sort the list so that those reviews are at the top. This appears to be happening on its own for the moment, though, and a small box even pops up if a friend has reviewed the business.

Back on Facebook, updates relating to Yelp-listed businesses can now appear in your feed, with a link pointing back to Yelp.

Lastly, judging by many people’s inboxes in the last several days, the new service has helped many Facebook friends become friends on Yelp.

Pandora

The instant personalization implementation on Pandora feels much less prominent than on Yelp. Like Yelp, the site notifies you at the top soon as you sign on that it’s connected to Facebook, but once you banish the notification bar it’s not immediately obvious where the Facebook connection is.

You might eventually spot the tie-in as you listen to your Pandora stations: if a friend is a fan of the artist or song you’re listening to, a bubble will appear to let you know. But unless you watch your Pandora window as the music plays, not to mention share similar music tastes with your friends, you’ll probably never notice.

The real integration takes place in the lower right-hand part of Pandora’s front page, where there’s an option called Friends’ Music. Clicking on this gives you a large box showing each friend and allowing you to navigate through to look at their music and, if you’d care to, listen to their stations.

Although Pandora seems less intent on bringing Facebook into its existing experience than Yelp, it may have just as much potential. For starters, Pandora has a larger userbase — I found 27 friends on Pandora, while only three were on Yelp. And seeing the music tastes of friends taught me something about them that I wouldn’t learn on Yelp (a certain male friend, it turns out, enjoys Miley Cyrus).

Pandora can also pull in some useful information from Facebook. For instance, if you “Like” a song in your Facebook profile, Pandora can see that and may play a similar song the next time you log on.

Docs.com

Microsoft’s integration with Facebook caused an audible ripple through the crowd when the screenshot flashed up on the screen at the f8 keynote. But the reaction was more the result of seeing a new alliance between two major companies, and the potential slap to Google Docs, than any immediate recognition of why Docs.com would be particularly useful on Facebook.

There’s also a significant difference between Docs.com and Yelp or Pandora: the latter two sites have an established presence of their own, while Docs is still in private beta testing. Further, its own descriptions of the service suggest that it expects Facebook users to mostly stay on Facebook itself to use Docs.

Still, there are a few notable points where Docs has brought Facebook into its fledgling site. Once you’ve created a new file on Docs, you can quickly grant individual friends or your entire Facebook network rights to view the document. Back on Facebook, the document will enter your feed, where it can be commented on like a photo.

Docs will also show you friends’ documents on its own site, and shows your Facebook friends in its right-hand sidebar, just like Yelp. All of these features have the same consumer-oriented feel as Facebook itself, which suggests that Microsoft may plan on popularizing its new site through the consumer channel rather than its enterprise client base. It’s easier to imagine kids sharing homework on Facebook than a corporate employee sending sensitive documents the same way.