Even sweet old Radio 4 is getting in on the act; last night I heard them encouraging people to use the hashtag #r4riot and join in with one of their live shows.

But my favourite example recently is Riz Ahmed, an actor in Four Lions, tweeting live (simultweeting?) along with a screening of the film on TV. What a great way to spread the word and encouraging re-watching. It’s a bit like the audio commentaries you get as extras on DVD, but much more vital.

Usually in these cases, there is a web-savvy way to deal with the wild west of social media, but in the case of the viciously satirical fake BP PR twitter account, I confess I’m at a loss what I’d do. Sample tweet:

We honestly didn’t think this was going to be a huge deal. No one cares when this happens in Nigeria

Not that I have any sympathy with BP over this, but if you were given the brief of responding to this (and assuming you’d accept the gig), what would you do??

Some of this is the simple fun of working within short sentences – the Twitter equivalent of OMG! txt spk – but I think hashtags mean something more.

Hashtags allow people to join a virtual club easily and temporarily. And to leave it just as quickly. People can just dive into a conversation, make a pithy observation about the #brits and dive right out again. No need to subscribe to an email list, no forms to fill in, no facebook group to join. It can be a no-complications, one-tweet stand.

They are perfectly suited for an world where attention is ever-more scarce and people are wary of sharing personal data. But they’re also wonderful fun – the ideas flitting in and out of existence in perfect harmony with their true value and popularity.

They’re hashmemes if you like.

Right now #oscars is in vogue but once the red carpet is rolled back up, it’ll disappear as a living idea until the next time enough of us shine a torch on it.

Hashtags.org allows anyone to see what’s hot at any moment, and even includes graphs describing most hashmemes’ beautifully short lifespans.

Marketers have to work pretty hard to jump on such fast-moving bandwagons. Indeed the only way to do it is to keep running. Only if you’re already up to speed with the conversation can you expect your brand to contribute something useful and credible.

And no-one will care.

Simply ‘being on facebook’, ‘having a blog’  or ‘getting a Twitter account’ won’t make your brand cool. In fact, get it wrong and it’ll be brand negative – like your dad dancing. Wearing a baseball cap. On backwards.

This is not because new media is a voodoo understood only by the geekorati. Far from it. As always, it’s about applying brand basics to new opportunties.

1. Own the category

Good brands know all about laying claim to the broader territory they operate in. It shows confidence, assumes leadership and educates consumers and customers alike.

Let’s say you sell coffee. Don’t make your blog just about your product activity. That might be fascinating to your colleagues, but not to the rest of us. Broaden your thinking and write about great coffee generally. About the bean growing process, about the best home espresso makers, about the Sunday papers and capuccino moment.

2. Know your brand

You know that old exercise about “if this brand were a car, what would it be” or “if it were a film”? Well, you’re going to need to know the answer to these questions. Knowing your brand’s tone of voice and view on the world is essential if you’re going to convincingly take part in online conversations. Southwest Airlines and Dell are getting it right.

3. Be where your customers are

It’s good to have a forum on your website and engage with people. But it’s better to be elsewhere too. You should come across as passionate and really taking part in the community. Practically, this means taking part in conversations wherever they happen, not just on your doorstep.

Get involved in whichever forums your customers use, no matter who runs them. But that does mean genuinely making a contribution, not just talking up your products. It’s the difference between being a gatecrasher and taking beer to the party.