Trends in the hyper-paced world of Twitter make the catwalks of Milan look positively passe. Most don't last half an hour.
But they do provide an insight into what the world is talking about and, for some, they're serious business - even if they only reflect the obsessions of a tapped-in slice of society and have been known to be manipulated in support of a dirty joke.
Twitter lists the 10 most-tweeted subjects on their website as ''Trending Topics''. For marketers, that's prime real estate. If you can get your topic '''to trend'', for a short time you'll cut through the cacophony of tweets and put your message in front of 100 million active Twitter users - 5 per cent of the online population, but some of the most connected.
For everyone else, it's a fascinating display of human nature, the warts-and-all reality of what catches people's attention - but something that probably shouldn't be taken too seriously.
Twitter trending isn't just about popularity, otherwise everyday subjects such as the weather and late-running CityRail trains would trend forever. Instead, it's about topics that become suddenly popular. The faster more people tweet about something, the more it trends.
You can blame Justin Bieber for that. During the first half of last year about 3 per cent of all tweets were Bieber fans talking about their idol. To avert a permanent Biebertrend, Twitter switched the focus to traffic ''spikes''.
Any sudden news event, or any widely-shared experience, is almost guaranteed to trend, as are the names of the people involved.
Natural disasters, sports matches, celebrities in the news - especially their deaths - newly-released films and books and anything made by Apple. But there can be surprises, such as ''vuvuzela'' last year because so many people complained about them, or ''Laurel-Ann Hardie'', because people debated whether the woman's name was real [it is].
Trending topics are often hashtags, Twitter's system for tagging tweets with a keyword, because the hashtag is the only word common to all tweets on a topic - such as #eqnz for the New Zealand earthquake in Christchurch.
Hashtags often trend when they're used for fun, like when people suggest #oneletteroffmovies such as Apocalypse Cow.
Or, when they're angry, like the US political hashtag #f**kyouwashington. Or, when they're completely tasteless, like #thingsdarkiessay, which supposedly started as an insiders joke in South Africa but was obviously offensive.
Depressingly, for those of us who live online, many trending topics are about TV programs. Indeed, live TV has now become a shared experience as the home audience discusses the program via Twitter. You can even see the names of individual contestants in shows such as American Idol trend in sequence as they appear on screen.
Members of hacktivist group Anonymous have been so disturbed by the prevalence of pop culture trending topics that they've created software called URGE, the Universal Rapid Gamma Emitter [Twitter edition]. ''This is not a hacking tool nor is it an exploit tool,'' they stress. URGE allows you to select an undesirable low-brow hashtag, such as #jerseyshore, and automatically send large numbers of tweets using that hashtag, but with more illuminating content. That's called hashtag hijacking, and Twitter frowns upon it because it's essentially spam.
Also frowned upon is sending lots of tweets with the same hashtag but little relevant content in an attempt to get your topic to trend, and tweeting about every trending topic in sight in an attempt to draw attention to yourself.
A more legitimate method for getting topics to trend is to persuade Twitter's ''influencers'' - users with large numbers of followers who tweet regularly - to broadcast your message. Web services such as Klout claim to measure your online influence.
But it's rubbish. Researchers at Hewlett-Packard's social computing lab analysed Twitter's trending topics and discovered that user activity and number of followers don't have much effect on how trends are created and spread. Trending content often originates from traditional media sources, and is then repeated around Twitter.
''We find that the resonance of the content with the users of the social network plays a major role in causing trends,'' they wrote.
Trends take off almost at random, simply because they started when people happened to be in the right mood. A light-hearted topic is unlikely to trend if the day's news is about a terrorist attack.
Or, conversely, a ridiculous topic might trend simply because it spread faster than a more serious one.
Yahoo! researcher Duncan Watts warned markets off wasting their money on social media influencers in 2006 for these same reasons. It's too unpredictable. Buy TV and newspaper advertising instead, he suggested.
I demonstrated this myself in 2009 when, for a laugh, I caused a certain sexual practice, that I won't name in a family newspaper, to become the number one trending topic globally in less than an hour, simply by asking people to use a smutty hashtag.
A boring Saturday night, a longstanding tradition of Aussie disrespect and the sleaze factor created a perfect storm that night, but a similar attempt a week later failed.
That particular experiment couldn't be repeated today. The surge of sleazy tweets would still count as a post-Bieber traffic spike, but Twitter now filters its trends for profanity.
HP's researchers reckon few trends stay at the top for more than 40 minutes. Indeed, trends are usually so short-lived that you can see them repeated hourly as the TV programs that triggered them followed the time zones.
The only reliable way to get a topic to trend is to pay Twitter for a ''Promoted Trend''. But how tacky is that?
Stilgherrian is a writer, broadcaster and prolific Twitter user with 6175 followers. He changed his name by deed poll and does not have a surname. Twitter: @stilgherrian.