In South Africa many ISPs offer something called Business ADSL. Its attributes are much the same as any other plain-Jane ADSL except that the package has static IP addresses. So in the minds of these ISPs, business equates to having a static IP. I suppose a business might have a mail server or web site but then so might anyone else! And often you can use a dynamic DNS service instead of a static IP to service the requirements of a mail server or website.
Read the article here.