Obviously it wouldn't make sense for people who only use micro instances, but then again people who only use one micro instance don't use a third party cost management tool.
Yes this is correct. Those numbers are based on data published at http://www.newvem.com/topic/cloud-radar. For reference, light user are those with up to 8 instances, medium users have between 9 and 35 instances, and heavy users above 35. We didn't publish the total number of users in each segment, but I can confirm that that the survey was based on a sample of around 200 customers, as mentioned in GigaOm's article
The reason we chose to segment by number of instances is that we consider this as a good metric for the complexity of one's cloud footprint, and the corresponding effort required to manage this footprint.
Well, of course it's a sales pitch in this context, that's why there is no actual data to back up their claims. But it stands to reason that customers using a lot of instances for high traffic sites can generally budget closer to the actual demand compared to small-timers who probably make up a large portion of AWS customers.
Obviously it wouldn't make sense for people who only use micro instances, but then again people who only use one micro instance don't use a third party cost management tool.