When you have your own business it is important that you have a list of your potential or existing customers. Finding new clients is important, too, and that's why having a marketing list is also a must.
My cousin works for a multi-national company, and they have their own consumer mailing lists which they try to keep in touch every now and then. I believe that they also ask for their customer's birth dates, and try to send birthday wishes yearly. I know some companies do that because I, too, receive birthday cards from some of the companies wherein I patronize their products. I personally think it's really great, since it makes you feel like you are special! :)
There are different list brokers that you can hire if you want a list of potential customers for your business. In fact, I believe that TLCLists.com is one of them. If you want to increase your current mailing list, then I suggest you go and check them out!