Most investigators would avoid this technique but you can count on some people using it. While you can find a lot of information by using internet research techniques, in fact, many of the SPAM messages offering to sell the program are scams, designed solely to take your money. While some do actually deliver a CD they make bogus claims. Perhaps you need to buy the software to figure out who they are because they don't seem to exist in the real world or in cyberspace. To say the least, Internet investigation is a young and developing fields.
Privacy issues continue to grow.
Technology will continue to race ahead with advances in both the investigative and privacy fronts. A number of companies are working on new tools that will give you even more control over your online privacy. However, so much information exists already that it won't be hard to find you. SpyWorld - privacy resources, equipment and books. The Anonymizer offers a number of services to cloak your identity.