Facebook users didn’t seem to have a great 2009 according to data the firm has just released. The biggest trends among status updates included celebrity deaths, swine flu, and general depression.

You’ll probably be seeing reports on the data in a variety of outlets today, but many of them are incorrect. The phrases and topics in the list are not the “most mentioned” words or phrases as is being widely reported.

For those of us who are geeky enough to read Facebook’s explanation of the data mining process, it emerges that simply looking at the most used terms (of one to four words) gives generic comments. For example, “just got back from” replaced “is looking forward to” as the most used four-word phrase. About the only thing this tells us is that Facebook users may have used the site more for reporting on events this year, rather than simply for arranging future ones.

The list instead comes from looking at which terms had the biggest proportional increase in use between last year and this year, hence “trends” rather than “popular phrases”. Facebook also categorized different phrases into single trends where appropriate.

Number one in the list was updates relating to Facebook applications, driven largely by the increase in use of games such as Farmville. And if you thought this was a passing fad, you might be wrong: the firm which produces the most popular of these games rakes in $100 million a year.

Things then get depressing (or more depressing depending on your view of the games) in slots two through four, which are held by FML, swine flu and celebrity deaths respectively. For those who don’t speak the lingo, and bearing in mind we are a family-friendly site, the acronym has a meaning along the lines of Forgoodnesssakeiamsomewhatdisappointedin My Life.

Most of the remaining phrases in the top 15 were generic topics (family, sports, movies, religion), while healthcare made the list thanks partly to a brief meme to update statuses to display a message beginning with “No one should have to die…” There were also a couple of statistical quirks on the list: mentions of the years 2008, 2009 and 2010 rose in popularity for obvious reasons, while a rise in the use of “I” was less to do with blossoming egos and more to do with the removal of a mandatory “is…” at the start of updates.

Facebook itself made the list, as did Twitter (probably through status updates along the lines of “…will no longer try linking his Twitter and Facebook updates. What a disaster that proved to be.”) And the only individual in the list was Lady Gaga: again, not because she was most mentioned, but because she showed a great increase in mentions having ascended to fame rapidly.

The site also provided timeline graphs for each of the top 15 phrases, throwing up some interesting stats and patterns. New Moon, Harry Potter and Star Trek were clearly the most popular movies of the year among Facebookers. Patrick Swayze’s death initially had around two-third the interest of Michael Jackson’s, but didn’t hold that interest for as long; Facebook suggests this is down to a lack of mystery about the cause.

And swine flu interest consistently peaks on a Wednesday. One theory is that people pick up the virus when returning to work on a Monday, with the symptoms showing two days later. A less charitable idea is that people are most likely to be looking for a reason to take time off in the middle of the work week.

And the biggest quirk of the entire list? Yard. At first glance this might appear to be down to some sort of fad for a piece of youthful slang. However, the stats show the phrase was most popular between May and September, suggesting it is literally referring to a yard, most likely because more middle-aged and elderly people are using the site and mentioning their outdoor activities in updates.