I'm also not getting where you're coming from Muel. It's not like he's advertising bras or something completely irrelevant, it's a phone and chances are he's got a phone and most likely (now) it'll be a Windows phone which does phone things just as well as any others. Using Danny, or Beckham or Lewis Hamilton to advertise anything is just supposed to make it appeal to a certain audience (in this case young, hip(!) people who know who that guy on the bike that rode over a spiky rail is and the chance to 'go viral' and get shared and posted worldwide for a huge amount of free advertising. I think they probably succeeded on that front and chances are the coverage they'll get will be massively increased because it incorporated Danny doing one of his stunts.
It's not selling out it's making the most of what could be a relatively short career at the top of his game and picking up support from some very big names, whether extreme sports related or from companies who maybe would like to jump on to that bandwagon.