I ask this because I used a Youtube video in a post that got a lot of attention about a week ago, I wrote about that post here: My Paranormal Life got farked, I went into a little detail about the effects of using a Youtube video in a post that gets popular.
I thought that I would expand upon this. I think that the main reason I didn't get any residual traffic from this post was because I used the youtube version of the video, I did find the Google video version first, but I searched for it on Youtube because I knew there would be a lot more discussion about the video there and subsequently used that version.
What I saw happen was instead of people staying and commenting on my blog and linking to my post, people would just click the Youtube video player, go to Youtube and join the discussion there and also probably link to that version instead of my post.
I think this could be true for most posts with Youtube videos in them, popular or not. People will move to youtube because there is bound to be a lot more discussion about the video there than on your own blog post and if they have a blog or site could easily share it themselves, cutting out the middle man.
Now what I intend to do in the future is if I find a video that I want to write a blog post about, I'll search for an alternative to the Youtube version, google video is a good bet, the only problem there is they have youtube results integrated into their search, but there's an easy work around to that which is to go to "Advanced Video Search" and once in there paste video.google.com into the box next to the "Domain" Option, this will only give you results from Google Video.
The reason for using an alternative from a site such as Google Video is that it is harder for the user to skip your post and go to the source, also there really isn't any great community interaction there, so there really isn't to much reason for the user to go there.
I used a a video from Google Video in a post awhile ago that was also popular and it generated a lot of traffic, now because people couldn't easily leave my site and go to the source, I found that other bloggers linked to that post and a few other major sites did as well and the residual traffic that that created lasted weeks. The traffic that this recent Youtube video post bought in only lasted a few days and had barely any link backs to my post.
Using Youtube Videos in your post could likely have an effect that you as a blog author may not like, you want visitors to your blog to stay on your blog, Youtube enables them to easily leave your blog.
I'll still use Youtube, a lot I think, but the above is just a little to think about before you use their service.