So I was setting up a Google campaign for my brand new SEO Index website. Essentially it is a directory of SEO tools and things like that. When I entered "SEO" into the Google AdWords Keyword Sandbox it stated
Here are additional keywords to consider:

search engine optimization
rankings
lesbianas
anal
positioning
pageoneresults
定義
relatos
lee
follar
advantage
firms
buscador
amater
...

If Google is that far off in determining what exact words are in the same community as the words you are buying, then odds are your user does not know exactly what he wants either. The words you are buying may not be targeted enough...