The DDOS-for-hire company doesn't need a significant or even continuous web presence, does it? Seems ineffective to DDOS them.
EDIT Surely many of these DDOS-for-hire companies cross into illegal territory. CF can maintain a content-neutral stance by kicking illegal activity off.
The DDoS-for-hire being discussed here are called booters. Access to them can be bought for a few dollars (~$10), and then one is able to log into the site and click a button to attack someone for a few minutes (the exact time depending on the booter itself and sometimes how much you pay).
EDIT Surely many of these DDOS-for-hire companies cross into illegal territory. CF can maintain a content-neutral stance by kicking illegal activity off.