So, this is a new fact about SharePoint for me – HideCustomAction Feature element doesn’t work with the EditControlBlock. Normally, you add links to menus, toolbars, etc., using a ‘CustomAction‘, and hide them using ‘HideCustomAction’. Works a treat in most of the interface.

However, with the Edit Control Block (ECB) Hide custom action doesn’t work. It looks like ‘cos the menu is rendered by JavaScript, you can’t hide them. Liam Cleary posted a good article about it for SharePoint 2007, and I suspect this will be the same in 2010. It means you’re likely to have to use JavaScript to remove things off the menu

Don’t know how I managed to avoid this problem for 4 years!