One question that sometimes comes up is about an artist or song that the user expects to see but cannot find. If there is a missing hit track on an artist's page then that needs to be fixed, however if you can't find a particular artist that could be legitimate (but, have you looked in the site index?).
For example one user complained that they couldn't find the artist "Puddle of Mudd" who had a hit in 2002 with "She Hates Me".
The listing on the site do not cover all the entries in the included charts, just the highest achievers. We list the top entries across the world from each year, all the songs of the 1000 top song acts, all the albums of the 1000 top album acts and all the songs that match the 1000 top song titles.
There are a two different motivations for only listing a subset of the complete data, firstly the copyright issues and secondly the site navigation.
The data here quotes values from a variety of sources, but, because it combines inputs it presents an "original work of authorship" what we have is a "compilation work" (see //www.bitlaw.com/copyright/database.html).
If we were to include all the entries of any one chart then the copyright owners could legitimately claim we were infringing their rights. Any user would be able to recreate, for example, the complete Billboard chart. While it is true that other sites, such as Wikipedia, quote source charts in full, we deliberately only quote a proportion of any of the input charts, for most charts much less than 50%.
In addition the value of these listings comes not from the contribution of any single input chart but rather from the level of creativity applied to bring together data from a variety of incompatible sources. The unique value of this site comes from the fact that it relates, for example a Billboard hit to its position in the Japanese charts. We strongly believe that any reasonable person would consider our listings clearly represent "fair use" of the source information.
Most of the 500,331 entries are just not interesting, more than 65% of all the chart entries only appear once in a single country's chart and are not even present anywhere else. The portion of entries that is included in the web site constitutes about 40-45% of all the song and album entries and covers about 25% of all the artists, however, for example, every album that has more that 10% of the top album's score has an entry on the site.
Adding the "less significant" entries would make it more difficult to navigate the site and, for the majority of users, would not add additional information that was valuable. Any user that wants to examine a particular chart in detail can do so on the original source. That is one of the reasons why we include links to the original data.