sublime1 - 11:53 pm on Nov 27, 2010 (gmt 0)
I agree with all comments here: 1) youtube is right for some sites, and certainly provides another opportunity to get clicked on in SERPs ... but it is not "professional" or within your control, 2) Amazon S3 and/or Cloudfront and a Flash Player or even some more modern iPhone/iPad compatible format work great, and are dirt cheap ... but provide little else, and 3) services that are designed to host videos cost a lot more, but you get cool stuff like analytics, heatmaps, and so on.
I would almost certainly use YouTube for a video I wanted the world to see. I would almost certainly use Amazon when I needed more control. I would almost certainly use an expensive service if that is what my customers expected. Depending on the site, I have found one or more of these methods useful -- there's no single right answer.
(Well, except for hosting streaming video because your cheesy self-hosting registrar account says for only an extra $20/month, you can :-)