The 600MM number is hostnames, the active site number is 186MM. At the end of the day, we don't really feel like hostnames (non-active, parked) are relevant.
There is a ton of spam on Weebly. We have a crowdsourced online shopping directory and 90% of the spam comments we get seem to involve Weebly sites. It's gotten to the point where we'll probably just write a simple spam filter that screens for "weebly" in our submissions.
Hey, we'd love to work with you on this. We have a full-time dedicated team that works hard on this and we have a zero-tolerance policy.
We work very hard to keep and maintain a high-quality network, and while the percentage spam is low across the network, even a low percentage can still be high volume for some.
Please email me (david+c@weebly.com) and I'll put you in touch with them, we are committed to taking a hard stance on spam.
I have 150 million webservers alone in Shodan (i.e. 150 million IPs with a webserver - completely ignoring vhosts), so 100 million seems rather low. Many of them are embedded servers etc., but there's a lot of web content out there.
According to Netcraft [1], there were over 600MM active sites [2] last month.
[1] http://news.netcraft.com/archives/2013/04/02/april-2013-web-...
[2] http://www.netcraft.com/active-sites/