Marina, I've created a new Youtube account today (for several reasons). Then I watched one of your older videos via a link to Youtube on a 3rd-party-side and subscribed your channel on that older video's page. When I went to Youtube's main page, your "Sergeant"-video, and only that video, was offered to me on top of the page in the "Subscriptions"-box. I've cleared cache and cookies before I created the new Youtube-account so Google could not verify that I've seen the "Sergeant"-video on http://www.hotforwords.com before.
Your "Sergeant"-video now appears on pos. 47 of the most watched videos.
When someone is watching one of your videos on http://www.hotforwords.com, Google/Youtube set - in response to the query for that video - some cookies on your website's visitor's computer. Here is a sample http-header returned by google:
HTTP/1.1 200 OK
Date: Tue, 17 Feb 2009 16:02:03 GMT
Server: Apache
X-Content-Type-Options: nosniff
Set-Cookie: use_hitbox=72c46ff6cbcdb7c5585c36411b6b334edAEAAAAw; path=/; domain
=.youtube.com
Set-Cookie: VISITOR_INFO1_LIVE=Y4YTTCe-JUY; path=/; domain=.youtube.com; expire
s=Thu, 15-Oct-2009 16:02:03 GMT
Set-Cookie: PREF=f1=50000000; path=/; domain=.youtube.com; expires=Fri, 15-Feb-
2019 16:02:03 GMT
Set-Cookie: GEO=9c1fe73ad6b36bf2697e991acc9698c3cwwAAAAyREXVJ8R4AHvfmkk=; path=
/; domain=.youtube.com; expires=Thu, 19-Feb-2009 16:02:03 GMT
Set-Cookie: watched_video_id_list=4cd761876fd012db7044a8bf54a65573WwEAAABzCwAAA
DZieXFOM3JpSlhF; path=/; domain=.youtube.com
Expires: Tue, 27 Apr 1971 19:44:06 EST
Cache-Control: no-cache
Content-Length: 154709
Keep-Alive: timeout=300
Connection: Keep-Alive
Content-Type: text/html; charset=utf-8
These three cookies are also set when someone is accessing the youtube-website directly.
Whenever I am accessing Youtube after having cleared my cookies, I am asked for my international preferences. I am not asked again until I clear all Youtube-cookies. Thus, these cookies are obviously used to reidentify previous Youtube-visitors and restore some of their user-preferences, even if these visitors don't use a Youtube-account.
Google has heavily invested in user-tracking techniques, and these techniques are in use on Youtube. Youtube gives every user a unique ID, stores what this user is watching under this ID and determines what videos to offer to that user upon what that user has watched before.
I wouldn't be surprised if Youtube would use this technique to identify that someone who is just logging in has seen the "Seargeant"-video before on your website so that Youtube doesn't have to offer it again in the "Subscriptions"-box. I must have a reason why Youtube sets a cookie named "watched_video_id_list".
But I'm not a Google insider and not even a cookie expert, I can only guess.