OK, this is probably a stupid question, but bear with me.. I'm on the Google Keyword tool at the moment, and in my niche, there is a two word keyword that has 21,000,000 global searches a month, and the competition is "low". Now, at the risk of sounding stupid, should I be trying to rank for that keyword? The reason why I ask is because it seems the obvious answer is yes, but then why is competition for that keyword so low? If anyone can shed some light, that would be great. Thanks.