[Evbn]

They are separate for user generated subdomains. http://www.seomoz.org/blog/understanding-root-domains-subdom...

It is possible that on that fateful day, Google noticed zlio is user generated sub domains, and lost power.

[allbombs]

technically you could still suffer from that.

subdomains are treated as separate domains, right

If all the subdomains had links back to zilo (say the header or footer), it starts to look like a huge link farm, or a bunch of satellite sites. It's actually pretty dangerous. But disavow is here, right? hah