This is one of those "my theory" posts but bear with me.
One of our sites ranks well (top 5 on page #1 of SERPS) for several popular phrases, some even single word phrases. In fact, one of the keywords is searched for approximately 85000 a month. However for another keyword phrase, we aren't in the SERPS *at all*.
The only pattern is that the MIA keyword is a popular legacy keyword. It is searched for about 105000 times a month, so that's only 20% above the well-ranking keyword, so the problem doesn't seem to keyword popularity related.
By legacy keyword I mean *not* a new keyword. For example, "widgets" (legacy) vs "ultrawidgets", if "ultrawidgets" was a new kind of widget that didn't even exist as a keyword a few years ago.
My theory is that Google has specific keyword penalties in their filter, left lying around from previous tuning attempts. Our site uses no black hat SEO techniques. For that site to rank well for so many keywords except for the one specific legacy keyword, indicates some kind of monkey business in the algo.
This site has been around for at least a year. Unless this is some weird kind of extended per-keyword "sandbox" (sandtrap?), it's very strange.
Anyone else seen similar occurences?