When I'm trying to do e.g. in either code or the Developer Console
SELECT Id, Type, Body, Title, ContentData From FeedItem where Type = 'ContentPost' LIMIT 1
No such column 'ContentData' on entity 'FeedItem'. If you are attempting to use a custom field, be sure to append the '__c' after the custom field name. Please reference your WSDL or the describe call for the appropriate names.
And indeed when I click 'Open Resource' and then FeedItem I somehow don't see the ContentData field being listed... Anybody an idea why not or what I do wrong?