Have you validated your market?

This post is a follow-on to this post where I asked "Are you solving a real pain?"  Entrepreneurs sometimes get caught up in believing in their own product so much that they really fail to validate the market before fully developing the product.  This also is sometimes referred to as "drinking your own kool-aid."  There are numerous ways to validate a market, depending on the type of product or service you are offering.  Let's say you want to offer a new widget for sale on the web.  Before you even spend a penny on developing it, how about spending a few bucks on a website that describes this widget, perhaps a little money to SEO it, and a button on your website that says "Click here for more info" and another button that says "Order Now" (which can return a polite message referring to order-backfill).  Even before you can fulfill any orders, you are collecting very valuable market data...all before you've spent a penny on developing possibly the wrong product.