If you want to keep your personal details a secret, you should not share information on the internet. If you do not have a business at home there is no point on sharing your snail mail address to the public. If you have your own business at home you could perhaps think about using a P.O.. Box to protect your personal snail mail address.
Cyber crime has many forms. Phishing to get your personal details is one of them. Other forms are viruses or worms that try to rob your personal information. Internet fraud happens in fraudulent auctions but not just in auctions.
There are many sellers and websites that sell products. And you should investigate the seller before you buy something. The only time when I was swindled on the internet was for $35,-. I bought an update for a script on my website from someone who created the script on my website.