I think the reason why so many WSO's are successful is because people can ask questions about the product right under the sales letter and the creator can actually reply back to them.
You can build a really good rapport with your potential customers by doing this.
Not only does this help the person who asked the question decide whether they want to buy the product, it helps other people who come along and have the same question decide if they want to buy too.
Not only does this format allow people who have questions to post right below the sales letter, it also allows people who have great things to say about the product to post under the sales letter.
Think about it, how many people actually go through the trouble of emailing you at your support email to ask a question? Chances are they don't.
However, if you gave them the option to post the question right there under your sales letter they would probably me more likely to ask it. If you required an email address for comments/questions you could then email them and tell them you answered their comment/question when you do, which would probably bring them back to your sales page.
Remember multiple exposure to a sales page leads to a better chance of a sale.
YET, not one sales letter that I know of does this! Can you imagine if you had a regular sales letter and allowed comments/questions to be posted under it?
Obviously, if it's on your domain you would probably want to moderate those comments/questions. However, this could probably improve your conversions by 300%+
What do you think?