Slogans come in two types, with barely anything in between. There are those, comparatively few in number, that one remembers effortlessly, with correct brand attribution, sometimes long after they have received any promotional expenditure. In this camp come 'Just do it', 'Because you're worth it' and 'The world's favourite airline'.
Then there is the other kind, vastly more numerous: the slogans that you can't recall a minute after you have seen them, and still can't attribute correctly even after they've been blitzed into your daily routine by the communications equivalent of formation bombing.
Which brand has just splashed out millions on 'New ideas, new possibilities'? Who has been telling us to 'Save today, save tomorrow' for three years now? Which corporate is 'For the journey'? If you have any of the answers at your fingertips, it's probably because you're actually working at Hyundai, EDF Energy or Lloyds TSB, respectively.
Slogans - of the first kind - are amazing brand assets, condensing meaning and texture into a bare linguistic fragment, evoking so much emotion precisely because they leave so much out. They were the original form of brand communication beyond the logo itself, punching out from bus-sides and shopfronts in the days when brands behaved more like bare-knuckle fighters than instigators of social discourse.
Perhaps because of that heritage, they are a less automatic inclusion these days. Modern marketers who shun the snappy verbal payoff take their cue from the success of contemporary, slogan-free icons such as Google, Starbucks, Amazon and Virgin.
In a fragmented media world, why don't these brands avail themselves of a proven, unifying communications tool? Are they simply above it, or could they be worried that they might undershoot and sully their reputations with a slogan of the second kind - bland, corporate and forgettable?
It is more subtle than that. You can bet that a great brand like Google, with smart marketers on board and skilled agencies alongside, could devise a stunning sign-off if it chose to: one of the immortals. In fact, that is the problem. Successful slogans are memes, invading minds, replicating and spreading without control. It is the inability to switch off the meme that scares brands that evolved in fast-moving industries and know the value of suppleness.
Immortality has its downsides. Look at BMW, which created one of the best-crafted lines of all time, and benefited from it for 35 years, then tried to abandon it in 2009. Why? Because research showed that the auto manufacturer's image needed to become softer. So up popped 'Joy', to take the brand to a less overtly masculine space.
The problem is, no one can erase 'The ultimate driving machine' from their consciousness. So BMW is doing what Heinz, Mars and Thomas Cook have done before it - accepting the inevitable and reverting to the words that made them famous.
The moral for marketers? If you're pondering the creation of a slogan for your brand, ask yourself why. If it's a knee-jerk, corporate thing, save yourself the effort. You will end up in the forgettable camp, with the equivalent of a grey blur under your logo.
A great slogan, by contrast, is the jewel in the branding crown, a verbal gem that commands attention, captures light and refracts the virtues of the brand with dazzling intensity. Like a real diamond, though, such a slogan is forever, so be sure you can live with it.
Helen Edwards has a PhD in marketing, an MBA from London Business School and is a partner at Passionbrand, where she works with some of the world's biggest advertisers
30 SECONDS ON ... SOME YOU REMEMBER, SOME YOU DON'T
Can you remember the brands?
1. Just do it.
2. The best a man can get.
3. Vorsprung durch technik.
4. Liquid engineering.
5. Because you're worth it.
6. Bean meanz _____.
7. The world's favourite airline.
8. Keep walking.
9. It does what it says on the tin.
10. Finger lickin' good.
Or the brands behind these slogans?
1. Stay you.
2. Feel better.
3. There's no better way to fly.
4. Driven by passion.
5. Have it your way.
6. Redefining standards.
7. Power to you.
8. It's you.
9. The diamond standard.
10. So good.
1. Nike 2. Gillette 3. Audi 4. Castrol 5. L'Oreal 6. Heinz 7. British Airways 8. Johnnie Walker 9. Ronseal 10. KFC
Not so easy
1. Holiday Inn 2. Bupa 3. Lufthansa 4. Fiat 5. Burger King 6. AXA 7. Vodafone 8. Yahoo! 9. Finish 10. KFC.