If you want to delve deeper, there are variants on this to use in larger companies.

1. I have heard on the grapevine that Amazon deliberately uses error pages to test appetites for products and features — you click on it, get an “oops sorry page broken” message, and click away without a second thought: on a site that big, there are bound to be broken links. Behind the scenes, those clicks are being counted.
2. Consider the user’s reaction to a non-existent product. If you’re an early-stage startup, nobody minds. If you’re an established company, this might come off as unprofessional, unless you provide some sort of value on the landing page (free report? White paper? Something they can use) while at the same time collecting those all-important email addresses for those eager to try it when it comes out.