Tech Weekly podcast: Andrew Blum with a behind the scenes look at the internet

This week on Tech Weekly with Aleks Krotoski and Guardian technology editor Charles Arthur discuss profit warnings and dark clouds above the makers of Blackberry phones RIM (Research In Motion) and the announcement of a write down on the value of Microsoft's online advertising service aQuantive. Also Aleks talks to the author Andrew Blum about his new book Tubes: Behind the Scenes at the Internet which sets out to explain what the internet is made of and why it's important for us to think about how we purchase access to the web.