In reply to William.

WordPress is a consumer product – it’s unfair to expect ordinary users to have to understand this kind of problem.

But you do expect them to understand how to turn it on? What is the chance that anyone which installs the wordpress iphone app will know how to handle the "can not login" message it will get? What helpful instructions can the app give when the site might be in a different language?

people want to be able to publish from the smartphone and tablets and as long as wordpress admin is not mobile friendly enough they need to use the apps which use xml-rpc.