Last week we mentioned Twitter's top trends of 2009 and what they say about our culture. This week Facebook is the latest social network to release their trending topics for the year, in what is fast becoming a trend in and of itself. Facebook's trends don't quite play out like Twitter, and they show some of the essential differences between Facebook and Twitter, and say a little bit about how Facebook users see the world as well.

Facebook's trends were taken solely from users' status updates, meaning that they don't reflect shared items - one critical difference. On Twitter, the trending topics are aggregated from all tweets, including those with links; in Facebook's more structured setting, the trending topics are selected from one stream of information - one out of many.

The other clear difference is in how the topics are organized and presented. Twitter's list broke trends into categories and listed the top trends for each category. Facebook aggregated them into categories as well, but simply ranked the categories. Facebook's list tells us which categories were the most popular; Twitter's list gives us granular information about what made up each broad trend category.

One of the most interesting things about Facebook's trends themselves is that the most popular topic, Facebook applications, is self-referential; that is, Facebook is Facebook's most discussed topic. The same, most likely, cannot be said about Twitter; although a good number of people occasionally tweet about Twitter itself, especially when it's down or otherwise funky, there is a relative dearth of Twitter games in comparison to Facebook games, and of Twitter gamers in comparison to Facebook gamers. Games like Farmville and Mafia Wars are what's driven up that category of topics to the top of the list. Facebook itself also appears lower in the list, at #9.

Some of Facebook's trends, though, make absolutely no sense. "Yard" is listed as the 13th most popular trend, which even Facebook Lars Backstrom can't explain:

The last trend on Facebook's list, "I," which they tracked as a combination of I and is is interesting because it shows how a relatively small change in the user interface of a large social network can dramatically change the way that people think about what they're doing. Before March of 2009, when people updated their status, they did so in a box that appeared next to their name; this led to people frequently beginning status updates with "is." After Facebook status updates were redesigned, however, and that box was modified and the name removed, Facebook says, usage of the word "I" doubled almost overnight, ultimately jumping from an overall rate of 1% of all status updates to 2.5%, a 250% increase in the use of the word simply by changing the way that users were incited to provide a status update.

Ultimately Facebook's trending topics might be more interesting than Twitter's trending topics, since Facebook's are analyzed more deeply and reveal more about the underlying systems that tie together the world's largest social network. You can check them out in detail yourself at their blog post about Facebook Memology: Top Status Trends of 2009.