C-blocks indicate the host you are using:
# Class A - supports 16 million hosts on each of 126 networks
# Class B - supports 65,000 hosts on each of 16,000 networks
# Class C - supports 254 hosts on each of 2 million networks
So, if you can get individual A or B blocks, that is cool, but harder to achieve.
The benefits:
Google has stated:
* Near-Duplicate Content Filter = If multiple search results contain identical titles and snippets, then only one of the documents is returned.
* Host Crowding =
If multiple results come from the same Web host, then only the first two are returned
Now, you will find some people that will say, "well, that only applies if the filter is on." They are correct, however, the filter on is the default setting, and I challenge you to figure out how to turn it off. I tried, and gave up after 15 or 20 minutes. I highly doubt any surfer is going to go thru the effort, primarily because, why bother? They don't care.
The filter only will happen if the sites are going for the same terms.
But your links between your sites will be more valuable if on seperate C's. If on the same it doesn't hurt you (unless going for the same terms). But it doesn't help you, Google will see that almost as the same site, like an internal link instead of external.
So, the question is how do I get around this host crowding filter?
You have two options. You can put each domain on a different host, meaning you will have multiple control panels, multiple bills and billing cycles, multiple personalities to deal with . . . kind of a PITA.
Or, you can use
Got Web Host. We can give you multiple Class C IP's, with multiple nameservers. We also offer free SEO consultations with our dedicated and virtual SEO plans.