It is true that after Google YouTube is quickly becoming the next most used Search Engine (SE). As wonderful as watching a video can be it is often slower than to scan for the information that your potential clients may be looking for as text. This is why I recommend using videos sparingly.
Good websites allow visitors to find the information they want quickly. This is why it is crucial to make sure your content is targeted and concise addressing how you can help the site visitor today - ultimately this is what the site visitor is looking for - your help today.
The best videos are targeted to the topic and state their case in a very short amount of time. What do I mean by a short amount of time? - literally 30-seconds. Think of every online visitor as suffering from ADD/ADHD - Think bullet points.
Instead of adding videos to your website the better way to avoid slowing down your website is to run the video from YouTube directly. You simply have a link from your website to the video - this is common practice.
If you have questions feel free to contact me.