Please, review the following blog post on the subject: http://blogs.telerik.com/ToddAnglin/Posts/07-07-16/RadControls_on_iPhone_Part_1.aspx
The editor content area is an editable IFRAME element, which uses the Rich Text Editing engine of the browser under which operates. Unfortunately, iPhone Safari still does not offer Rich Text Editing support and that is why RadEditor is loaded non editable in this browser.
Once the mobile browsers provide support for RTF we will do our best to provide full editing support for them.
the Telerik team
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