There has to be a way to see all links pointing to your site...

Actually, there is not.

Any tool which provides a report of links to your site has to collect the data somehow. The most common means is to crawl the internet, collecting data on each page that is encountered. There are very few organizations which have sufficient resources to crawl billions of web pages and process the data in a timely manner. Google is by far the most efficient.

Even so, web pages can be blocked by various methods:

• the page could be on a member-only part of the site which requires a username and password to view. Such a page cannot be discovered by crawlers.

• the page could be tagged with noindex, nofollow to where the link is not discovered. It can also be blocked with robots.txt

• the link may be presented in an iframe, flash or other means which the crawler does not capture.

• the page may be buried so deeply on a site, or on an island page, where the crawler does not ever reach it.

In the above cases, a link to your site may exist but not be found. An excellent means to capture undiscovered links is using Google Analytics to determine the source of any traffic. This method can help you discover links to your site which otherwise were not discovered via a crawler.

If a link does exist but is not captured by OSE and is not sending you any traffic, the link likely has no value at all.

@Klarke, that WBF video addresses "link diversity" which is a related but separate topic.

IP diversity would address links coming from separate IPs.

Often a site owner, especially on shared hosting plans, have a single IP. They can host literally dozens of sites with that IP. When multiple sites link from the same IP, it is an indicator the links are not "independent votes" but rather the same site owner repeatedly "voting" for the same site.

In the early 2000s site owners were able to manipulate rankings in this manner. In the mid 2000s, search engines caught on to this type of scheme and began looking for IP diversity. Multiple links from the same IP were treated as less valuable or the links were devalued almost completely.

In the late 2000s, the concept of "C-block" diversity became important. IPs take the form of numbers such as XXX.XXX.XXX.XXX where the numbers are seen in the format of AAA.BBB.CCC.DDD. An IP of 150.76.44.255 would have a C block of 44. When IPs were assigned to various web hosts, the C block mostly remained constant.

Around 2010, search engines further evolved to keep up with the times. Presently it is easy for anyone to acquire a range of completely different IPs on the same server. Deeper analysis is required to catch manipulation from the same site owner. For example, often the nameserver will reveal other sites on the server, but that information can be manipulated as well.

The concept of IP diversity should not be thought about unless you are venturing into black hat SEO in which case your efforts will likely fail. For the relatively few people who get away with it nowadays, there are tons who are caught.