DoubleClick is very much the largest and awesomest exchange. But there's A LOT of display ads on the web.
The data we have suggests that DoubleClick offers up about 4b daily impressions to retarget against. The overall retargeting ecosphere that folks like us and a few others are retargeting against is in the 10-14b impressions/day range. DoubleClick's massive and have a lot of the best inventory, but it's still just a part of the whole.
NOTE: I'm sure there's other display-heads on HN who might have different data. Either way, Google's exchange is no more than 30-50% of the total exchange inventory out there.
The data we have suggests that DoubleClick offers up about 4b daily impressions to retarget against. The overall retargeting ecosphere that folks like us and a few others are retargeting against is in the 10-14b impressions/day range. DoubleClick's massive and have a lot of the best inventory, but it's still just a part of the whole.
NOTE: I'm sure there's other display-heads on HN who might have different data. Either way, Google's exchange is no more than 30-50% of the total exchange inventory out there.