Giving a seminar or presentation is an effective way to market your services. But - placing video of a whole presentation on your website is NOT a good idea. Why? Because people don't like to watch long, unedited videos. Even if your presentation is just twenty minutes, people are far more likely to watch shorter clips.
So - plan to extract the best short clips from your raw video, and then post those clips on different pages on your website. It's a great way to generate multiple video assets from one video shoot. And - it's a great way to use video to establish your credibility and expertise, and to differentiate your company.