As per Greg Niland who also has been in the SEO community for ages, stated that c-blocks and c-classes play a vital role in ranking. He has further noted that having links from IPs on various c-classes can also result in propelling the rankings. He has also written a post that depicts that Google would facilitate more link power if your links that are inbound are on various c classes IP addresses.
In recent times we have heard that Google is very strict about the IP addresses that fall in the c-class. However, one does not needs to worry by being on the same c-class IP address of a spammy website. But, at times, one can be in trouble if your website exists on 10,000 sites on a spammy C-Class. On the other hand, you also have been to be on the lookout for many link tools. It is so because these link tools differentiate the links that you obtain from unique C-Classes. It can be attributed to the reason that SEO strategies think that way.
This is the reason that many SEO strategists nowadays are wondering about the usefulness of natural links. This is the reason that one needs to have a clear picture about the C-Class links that one obtains from natural links.