Blackhole Routes

Hi, There are ways to add static routes that can be blackholed. I can understand the utility of such routes if those are installed in my forwarding table. What bewilders me is why would anyone want to advertise "blackhole" routes using say, BGP? Is it only to prevent some sort of DoS attacks or are there other uses also of advertising black hole routes? Thanks, Abhishek -- Class of 2004 Institute of Technology, BHU Varanasi, India