According to the Arbor Networks blog, Google properties have gained 1% of worldwide Internet traffic share since January (a record), to average 6.4% of all worldwide Internet traffic.
If Google were an internet service provider (ISP), it would be the second largest – in the world (and Google of course accounts for a large percentage of the largest ISP as well).
The post also says:
This number grows even larger (to as much as 8-12%) if I include estimates of traffic offloaded by the increasingly common Google Global Cache (GGC) deployments and error in our data due to the extremely high degree of Google edge peering with consumer networks.
While its not news that Google is Big, what is amazing is how much bigger Google continues to get. A quick analysis of the data also shows Google now has direct peering (i.e. not transit) with more than 70% of all providers around the world (an increase of 5-10% from last year).