Sar: https://secure.gog.com/game/blackguards_special_edition vs
http://www.gog.com/game/blackguards_special_edition Video doesn't work on the first page, which is the page you arrive at when viewing a game page from the checkout, but it does work on the normal page.
Just thought you should know :)
Likely depends on the browser and your security settings. The Youtube URL is set as http, not https, and some browsers don't like loading external resources from unsecured connections if the page itself is secured.
Personally, I use HTTPS Everywhere for Firefox to automatically use secure connections if possible, so I'm not affected (since the http Youtube URL is automatically converted to https).
GOG could just have started the URL with // though. Despite being non-standard, just about all browsers will add the same protocol specification as the page uses (https: in this case). Yes, even "ye olde" Internet Explorer 8.