Website owners can force telecom's cache to not cache their website. It works for apache and iis servers:
http://en.wikipedia.org/wiki/List_of_HTTP_headers#Avoiding_Caching
http://support.microsoft.com/kb/247404
http://www.i18nguy.com/markup/metatags.html
It just involves putting some html code into your apache or iis server and into your website and this will tell telecom's cache to not cache your website so visitors get a fresh up to date version of your website all the time.
Here is an example of youtube using the no cache header:
http://url-info.appspot.com
Type in www.youtube.com and click 'headers' once the scan is finish. You will see this:
Cache-Control no-cache
So i don't know how telecom is caching youtube videos.