The early December 2013 network snapshots, i.e. with over 100k nodes, are not valid as the crawler at that time took several hours just to complete one full network snapshot and it includes all nodes from addr responses which can be faked or likely stale. Those snapshots were linked to from getaddr.bitnodes.io/SNAPSHOT_NUMBER/ which have been removed since.
With the new crawler released in late Dec 2013, the crawl time was brought down significantly down to sub 5 minutes with considerably good churn rate. I use the churn rate to measure how good a network snapshot is. A value of 0 implies the network snapshot was taken instantly but of course that's not possible. At the moment, we are seeing a typical churn rate of 30+: https://getaddr.bitnodes.io/nodes/
With the new crawler released in late Dec 2013, the crawl time was brought down significantly down to sub 5 minutes with considerably good churn rate. I use the churn rate to measure how good a network snapshot is. A value of 0 implies the network snapshot was taken instantly but of course that's not possible. At the moment, we are seeing a typical churn rate of 30+: https://getaddr.bitnodes.io/nodes/
That's a definitive answer.
Thanks for helping resolve the issue.
This, and what Mike Hearn said about the crawler being more effective now. The crawler software was improved to only count nodes with 100% access and fully configured. It now looks at different parameters before it counts it as a full node. {If it's poorly configured and does not give full access, it will not be counted}
So there might be people out there, who have poorly configured nodes, and they do not even know it.
This should be addressed by the Bitcoin Core developers {Setting of default parameters, to automatically configure nodes to run at full capacity or minimum standards to be counted as a full node}
People just install the software and run the default options.
