Index: wp-admin/css/wp-admin.dev.css
===================================================================
--- wp-admin/css/wp-admin.dev.css	(revision 18179)
+++ wp-admin/css/wp-admin.dev.css	(working copy)
@@ -4270,6 +4270,11 @@
 	background: url(../images/press-this.png) no-repeat -45px 5px ;
 	padding: 8px 0 8px 32px;
 	display: inline-block;
+	user-select: none;
+	-webkit-user-select: none;
+	-moz-user-select: -moz-none;
+	-khtml-user-select: none;
+	-o-user-select: none;
 }
 
 .pressthis a:after {