Index: src/wp-includes/js/wplink.js
===================================================================
--- src/wp-includes/js/wplink.js	(revision 31168)
+++ src/wp-includes/js/wplink.js	(working copy)
@@ -187,9 +187,15 @@
 		},
 
 		getAttrs: function() {
+			var href = $.trim( inputs.url.val() );
+
+			if ( ! /^(?:[a-z]+:|#|\?|\.|\/)/.test( href ) ) {
+				href = 'http://' + href;
+			}
+
 			return {
-				href: inputs.url.val(),
-				title: inputs.title.val(),
+				href: href,
+				title: $.trim( inputs.title.val() ),
 				target: inputs.openInNewTab.prop( 'checked' ) ? '_blank' : ''
 			};
 		},
@@ -309,7 +315,7 @@
 				inputs.url.val( selection.replace( /&|&#0?38;/gi, '&' ) );
 			} else {
 				// Set URL to default.
-				inputs.url.val( 'http://' );
+				inputs.url.val( '' );
 			}
 
 			// Set description to default.