The social mobile web phenomenon with all those colluding superangels and bubbilicious valuations has been so far centered in two places: Silicon Valley (SF) and Silicon Alley (NYC). The Economist now reports that a third center has emerged: Silicon Roundabout in the east end of London:

In 2008 followers of the technology industry began to talk excitedly about a cluster of internet start-ups in the Shoreditch area, near the ugly Old Street junction, to the north-east of the financial district. There are now around a hundred high-tech businesses in what has inevitably been dubbed Silicon Roundabout.

Measured by the concentration of technology firms and the availability of generous and informed investors, California’s Silicon Valley is still in a league of its own. But in the second division of hubs, this chunk of east London is near the top, along with the likes of Boston and Tel Aviv. That its growth took place so quickly, and during a recession, is remarkable enough: the high-tech zone in Cambridge has taken decades to evolve. But the fact that Silicon Roundabout also emerged without government support, or even direct links with universities, should pique the interest of countries that have tried to cultivate technology hubs without the same success.

Techcrunch also reports from London, and depressingly found there was less here than meets the eye. The Economist story seems a bit out of date, as some of the Roundabout companies have left for other locales. The potential is still there, but it is been a bit of a flat year. A return visit found that the London petri dish is spawning a few successes, mostly around media.

There is a deeper story here. Observers of Silicon Valley have reported a cluster of forces led to its emergence: universities, venture capital, favorable employment laws, and a density of engineering talent. The Silicon Roundabout story has none of those attributes. How did it emerge so fast?

The Silicon Valley story fit an era of investing in core technology, which spun out of universities, and required heavy venture capital to get launched. The founders of social mobile web companies are working at the top of the technical stack, in the apps layer, where the tools allow rapid product development. They can be funded by angels and super-angels, and get far enough along in market traction to attract funding from VCs that need not be close by.

Simply put, this is no longer about technology, but about imagination.

What is driving Silicon Roundabut is the same phenom that started first South of Market Street in SF and second north of the Village in NYC: birds of a feather flocking together. The 20something Millennials who are driving the social mobile web like to live in cities, and their energy and co-opetition is feeding on itself to lead to long hours and cool products.

So where next? My bet is Silicon Outback: Sydney. It has the same attributes of a place attractive to Millennials, and shares a cultural affinity to social mobile web products. Get on it, down under, will ya?