Easy. 100 people are logged on to gmail from IP1 and someone(you) DNS-ing to naughty1.com 200 people later on logged on to gmail from IP2 and someone(you agai

Easy. 100 people are logged on to gmail from IP1 and someone(you) DNS-ing to naughty1.com 200 people later on logged on to gmail from IP2 and someone(you again?) is DNS-ing to naughty1.com. However among group of first 100 and second 200 users - only you are the common denominator. That would make it a high probability guess that you're been using that site. There are other things google can put together to narrow DNS user to persona