I think what people may mean is that you should not store the CC info on a publicly accessible DB. If you are going to store it in your own DB, the DB should reside behind a firewall and not be accessible from the public web site.
At first blush that sounds illogical- after all, if it's not accessible from the web, how do you get the info to the DB in the first place? Ah, Grasshopper, you give write access, but not read access, to the web application. Make read access only available from behind the firewall.
For the newbie who doesn't understand all the technical requirements or have the money to invest in the proper H/W & S/W, then local storage is obviously NOT recommended.