Suppose you have a page on your site that is a couple thousand words long. How would you determine when to split the page into two and are there any SEO advantages to doing this like being more focused on a specific topic. I noticed the Beginner's Guide to SEO is split into several pages, although it would concentrate the link juice if it was all on one page.

Suppose you have a lot of comments. Is it better to move comments to a second page at a certain point? Sometimes the comments are not super focused on the topic of the page compared to the main text.

I don't think you would get credit for your content if it was within an iframe and hosted on a different site like DotSub or YouTube. If you Google "HTML scroll box" you can find some good tutorials on adding an HTML scroll box. This should make it easy for Google to crawl and index the text content as part of your page but not take up too much space for human visitors.

If you also post the transcript on YouTube then I think this would be considered duplicate content by search engines. After the Panda update I would be cautious about having tons of duplicate content on your site.

One line of thinking is that you can not have too many words on a page because the more words you have the higher the chances that a long tail phrase will attract traffic. But can you go overboard with this? Is there a limit to the number of words on a page in terms of SEO?

I haven't paid a lot for a domain name but I would definitely consider 5 figures if the domain was an exact match for a really important phrase. In my experience Google still gives a ton of bias to exact match domains and if that goes away you will still have a strong advantage over competitors because people are likely to link to you using an important keyword phrase in the anchor text. When considering a price, I would suggest looking at the potential extra traffic you would get if you had the exact match. If you assume that the exact match domain will help you rank #1 for an important kw phrase, the ROI could be very good.