But you can get them to mirror one another.* [See update below - choose just one of these].
Feeding Facebook’s Status with all your Twitter updates is relatively easy. Twitter has a Facebook Application which now allows the integration of the two. Simply add the Application, the hit the ‘Want Twitter to update your Facebook status?’ option at the top of the page and allow the Application access to Facebook. Usefully it prepends ‘twittering:’ to your tweets to solve Facebook’s additonal ‘is’ in the status.
Feeding Twitter with your Facebook Status is more convoluted since Twitter doesn’t offer a reciprocal arrangement directly (that I can find). But it does have APIs – enter TwitterFeed. TwitterFeed will allow you to import any RSS content into Twitter – like your blog for instance. Or your Facebook Status. Finding the RSS feed for your FB Status is a little tricky. Here’s how – go to your Profile, hit See All on your Mini-Feed, choose Status Stories in the right hand sidebar and on the bottom right, you’ll see ‘Subscribe to these stories: My Status’. This is the RSS feed for your Facebook Status. Thanks to Jeff Sandquist at MS for this tip.
Now you need to log into TwitterFeed which requires an OpenID login. You may already have one if you have a Yahoo or WordPress account. If not, it’s relatively simple and free via IDProxy. Once in TwitterFeed, you can add in your Facebook Status feed. TwitterFeed only updates every hour, or every 30 minutes if you change the options, so this is not real-time. But it should mirror the two to an extent.
One thing which is interesting is which social network will end up as the ultimate publisher. Like others, I’ve used Tumblr as the aggregator of my Twitter, Facebook, YouTube, Flickr, del.icio.us and blog feeds on Morganutiae. This works as long as those are all separate RSS streams. Now they are starting to merge themselves, you get repetition at the top level on Tumblr. More importantly, which will become the departure site of choice. If you can get Facebook and Twitter to mirror one another – when it comes to status updates, it doesn’t matter so much.
*UPDATE - Getting both Twitter and Facebook Status to mirror one another actually turns out not work since they both end up self-replicating the same content in an endless echo chamber. Both of these systems work, but it should be unidirectional only. So it’s best to just choose the input interface you prefer and get that to propagate to the other.