Preventing automated comment spam in .NET web apps without CAPTCHAs

We all know the problem of automated comment spam, not only for blogs, but for every web site requesting information from the user which is published directly on the website. When you are asked to develop a site where you could encounter this problem, there is a pretty easy way to prevent it, without resorting to authentication or CAPTCHAs. I hope this post doesn’t inspire developers of automated spammer software…