The more time I spend around web services, the more I see 2% conversion rates show up all over the place. About 2% of people who visit a WordPress.com blog leave a comment. 2% click on “related articles” below a blog post. 2% of Evernote users buy their premium service. Same with 2% of Box.net users. We see similar numbers with WordPress.com premium upgrades. Is this a coincidence, or is there an underlying law that drives this? If you put something for free on the Internet and ask people to engage and take some sort of action, 2% of them will do so on average? I say on average, because I’ve seen 1-5% ranges on various services, but the 2% number seems to be the most common.