London is Facebook’s top network

London has usurped Toronto as Facebook’s most popular network. More than 750,000 people have joined the network, almost half of them since May.

The web phenomenon of 2007 recently signed up its 30 millionth member, 790,615 of which admit to some kind of affiliation with the UK capital. The UK has 2.1 million Facebook users.

Facebook said it could find no specific reason for the popularity of London, noting only that the growth of the network matches “overall pattern of growing exponentially”.

Part of Facebook’s appeal are the plethora of third-party “applications” that developers have plugged into it. They range from the banal – such as virtual food fights – to the cerebral – online Scrabble – but have allowed the site to grow without having to make expensive acquisitions.

Last week Facebook announced its first purchase, Parakey. The company, founded recently by former Firefox engineers Blake Ross and Joe Hewitt, is developing a platform for building web-style applications that run offline – a kind of web-based operating system.

Whether Facebook survives long enough to put that into practice remains to be seen. What is fashionable one year may not be quite so compelling several months down the line. And it may yet be shutdown if it fails to win a US court battle this week over exactly who came up with the idea – and the code – for the site.