Computer Weekly: The US Internet securty organisation CERT has published a warning of increasing DRDoS (Distributed Reflection and amplification DDoS) attacks using Internet Service Providers’ NTP (Network Time Protocol) servers (http://www.kb.cert.org/vuls/id/348126).
According to their analysis NTP is the second most widely used vehicle for DDoS attacks (after DNS). In plain language that means, if I want to take a victim web site down, I can send a spoofed message to a vulnerable ISP NTP server and get it to send a response that is several thousand times longer to my intended victim! That is amplification in action.