Are there ways to measure how much of the traffic is actually due to reddit being out. I bet there are other reasons for the growth in traffic, like the fact th

Are there ways to measure how much of the traffic is actually due to reddit being out. I bet there are other reasons for the growth in traffic, like the fact that HN has been making a great job at covering SOPA/PIPA for the past few weeks, I wouldn't be surprised if part of the increase is due to natural SEO. I'm sure one could find other reasons too. I'm not doubting pg's claim. I'm simply interested and curious: What are the tools available for the analyst/engineer/community manager to analyze the increase?