Speculation surfaced this weekend that Twitter has been censoring the discussion of WikiLeaks by keeping it out of trending topics.

According to Twitter, the list of trending topics is determined by the words, phrases or hashtags appearing in the greatest number of tweets at any given time. Given the flurry of news about WikiLeaks since it released thousands of secret U.S. embassy cables last weekend, it's a little surprising that #WikiLeaks has been entirely left out of Twitter's Trending Topics list.

It's especially surprising when you look at the data compiled by a blogger known as Bubbloy, who pulled data from trendistic.com that shows that as of last night, #WikiLeaks was outperforming the top five Trending Topics on Twitter, yet it did not make the list (see graph, below).







In fact, according to his data, #WikiLeaks hasn't been a trending topic since August 21, although #cablegate was trending last weekend.

Over at the blog Student Activism, which has also noted #WikiLeaks's conspicuous absence from the Trending Topics, a commenter who claims to be Twitter Product Manager Josh Elman (Update (1:37 p.m. ET): Confirmed: It's him) offered this explanation for #WikiLeaks's absence:

"Twitter hasn’t modified trends in any way to help or prevent wikileaks from trending. #cablegate was trending last weekend and various terms around this issue have trended in different regions over the past week. Trends isn’t just about volume of a term but also the diversity of people and tweets about a term and looking for organic volume increases above the norm. I hope this helps."

It is therefore possible that #WikiLeaks is failing to trend because the tweets simply aren't diverse enough in content, although looking at the current list of tweets with the hashtag #WikiLeaks, this seems a little hard to believe.

Twitter Director of Communications Matt Graves likewise denied the allegations that #WikiLeaks is being censored: "Twitter is absolutely not keeping Wikileaks out of Trending Topics," he wrote to Mashable.

This is not the first time Twitter has been accused of keeping certain hashtags out of Trending Topics. Last week, student protestors at University College London (UCL) complained that the microblogging service was keeping the hashtag #demo2010 off the list, and that Twitter even went so far as to make their accounts unavailable. Twitter likewise denied the allegations.

As a side note, Twitter's communications team has repeatedly dodged questions about whether it will continue to allow the @WikiLeaks account to run on the service after EveryDNS.net, Amazon and PayPal terminated their service contracts with the organization, citing illegal activity.

Update (1:20 p.m. ET): Twitter has just released the following statement: