CloudCamp 4 London took place last Thursday in Microsoft’s offices at Victoria, continuing on success of the previous meetings. From what I could see, about 250 people attended, and the main overarching theme for the lightning talks this time was data security and using clouds for data storage. Here's a write-up from the event: http://gojko.net/2009/07/13/cloudcamp-london-4-dealing-with-data-security/