I did some keyword research using google keywords tool and free version of traffic travis last week. Found some good buying keywords, for a website I want to set up, with low SEO competition. I went back and checked these keywords 2 days ago and everything had changed many went from being 'relatively easy' to rank (according to Traffic Travis) to 'medium difficulty' or 'difficult'. Quite a change in just a few days. Have checked them again today and many of them have changed again. I don't whether I should be targeting these keywords or staying well clear, they seem so volatile! What's going on here, how can the SEO competition change so rapidly in a short space of time? How can they be easy keywords to rank one day, difficult the next and then easy the day after?