While in the store, some people will go online and check their email and other personal accounts. Some people will even check their banking data on these computers. This is very dangerous for many reasons.
Being online can be a problem when it comes to black hat hackers and other types of bad guys. But that is not the only place that you have to worry about your credit card.
The one thing that you can say is that Facebook really does try to keep everything in order on the web site. When they find someone has corrupted the system then they do their best to try and fix it.
