Reputations used to take years, if not decades, to build. Now, they can be won and lost in seconds as Toyota, Eurostar and countless other companies have recently found to their cost. 

The last few weeks have proved that social media is a hard-news gossip zone. Twitter, in particular, works at its best when tweets contain a fresh fact, an exciting news update. The issues that trend strongly are those that Twitter followers want to retweet because they're so newsy.

The ash cloud is a strong example. It was an event that affected millions of travellers, and businesses, globally. The path of the cloud was changing rapidly and channels such as Twitter were ideal for updating travellers quickly about the latest schedules and plans of airlines, airports, car hire firms, ferry and train operators. Yet, many in the travel industry didn't use Twitter effectively at all. They couldn't respond quickly enough, or didn't have the right agency structure in place to advise them.

The ash cloud crisis proved that digital agencies can't do social media. Many of them are employed to build and maintain social media channels for companies yet, because digital agencies generally don't employ former journalists, they don't have a clue how to react to major news events. Crisis PR agencies generally do.

Social media is rapid. Twitter indexes every 45 seconds whereas Google takes at least an hour.

Secondly, it's viral. Advertising content rarely jumps across media because it has to be paid for. That's why above-the-line spend is so exposed to social media's lightning charge.

As it is viral, social media is also highly credible. No amount of advertising or content from Toyota could save the brand from horrendous stories of families suffering from brakes being jammed because the stories on social media are source-based. Crowd-sourced content is third-party and therefore more believable.

Social media is international. It therefore emerges 24 hours a day, seven days a week. Every corner of the globe feeds into social media.

Finally, social media is structurally and culturally different. It is designed for the news-alert professional. Digital marketing agencies are relaxed places where people listen to iPods and brainstorm. They interact with their clients on a project basis, not every day. They have little experience of a crisis because they've never worked in that environment.

A good crisis agency, who shines at social media and employs journalists, has the ability to deploy "go" teams to any part of the world in hours. Digital agencies wouldn't know where their passports are.

Companies which ignore social media are placing their entire brand equity at risk. At the very least, social media is brand equity insurance. Many organisations' budgets, plans and, importantly, shareholder dividends, have been blown away because of a lack of understanding of the power of these channels. Boards can only ignore this at their peril. When they wake up, they need to choose a PR agency that knows how to handle a crisis, not a digital marketing agency that thinks tweets are just about sales messages. Don't let anyone tell you otherwise.