 <p>It's not necessarily "more secure".</p> <p>It's just more convenient. Imagine you have more than one web service in your organisation. The client can use the optained token to prove his identity to all of those services.</p> <p>I recommend reading this <a href="http://msdn.microsoft.com/en-us/library/ff650503.aspx" rel="nofollow">article</a> for further information.</p>