At any time, there's usually only one company that's obviously King of the Valley. Years back it was Netscape. Then it was Yahoo, then Google, then Facebook.

Now, arguably, it's Twitter, the social web service where you declare what you're doing in 140 characters or less.

What's odd, though, is that to be top dog here you needn't be the Valley's biggest fish or the dominant player in the particular niche you're pursuing. You needn't even have invented your niche, and you certainly don't need to be making money.

All you really need is buzz, which leads to growth, which leads others to add on services to your own, which brings more growth and, you hope, finally, riches. But how to get that buzz? With hindsight it seems obvious why Google, Yahoo and Facebook got noticed, but when they were first declared hot, things weren't so clear.

Twitter's a particularly dramatic case. What it does is simple - other services do pretty much the same - and a great many people think it's a useless waste of time. So how come Twitter grew by an astounding 752% in the last year?

Well, it's a little like surfing. You need to have the skill to surf a wave. But you also need the good luck to be in the right place when it arrives. Twitter hit the social networking wave just right and is riding it very nicely, thank you.

The Valley ecosystem is an operation that makes big-time bets on start-up surfers. We expect wipeouts. But there's glory to be had for the champion wave-riders, and for anyone who backs them.