You pretty much post your bank account numbers evertime you right a check.
And, people print ALL SORTS of stuff on their checks, like SS numbers, phone numbers, driver's license numbers, etc. They also supply that information to any clerk at a check out that asks.
And, worse than checks, we give out our CC numbers everywhere also.
I once watched a group of guys that were angry at another person (there was a sale of some truck parts and the guy who sold the parts sold junk and refused to refund the money). This particular site polices their own as far as selling junk, refusal to pay, etc., and they can get rather rough.
As the forum debate started out, people started calling out the bad seller. When he refused to cooperate -- or even work out a solution (and worse, he started really bad-mouthing the entire forum, etc.) some people started to coerce him. They began by listing his real name. Then his address. Then pictures of his home. Then pictures of his wife and kids. Then his phone number.
Then, one post at a time, his credit card number -- one number per post. By the time they got to the second set of numbers, the guy decided that he was going to be wiped out and he made right on the sale. This entire episode took under 20 minutes... It was fun to watch, but scary also.
I recommend lifelock - the protective service that watches over one's identity.
http://www.lifelock.com/
I also recommend that everyone pull their credit reports once a year. Don't go to that "Free Credit Report" dot com place. They are a rip off and only want you to give them your card number. Instead, the government has authorized a free credit report per year which is available at
www.annualcreditreport.com This will redirect you to a Federal Trade Commission site where you can pull all three of the major credit reporting bureau reports for free with no strings attached.