A reader wonders: Can you tell me what the harm is in putting in more key words than less key words since a person only gets charged for the clicks on Google when someone actually clicks on your ad?
Howie answers the wondering:
There are two potential problems with huge keyword lists:
1. The Quality Score Problem:
If you have a lot of very low CTR keywords, they will tarnish your entire account’s quality score. Google has an opinion, not only about individual ads and keywords, but about your whole account. After you’ve been running AdWords for a while, Google develops an opinion of you, and either gives you the benefit of the doubt or not whenever you throw something new onto AdWords.
2. The 80/20 Principle Mountains of Junk Problem:
If you have thousands of keywords just for the sake of having more rather than fewer, you run the risk of losing sight of the 5 really important keywords that should get 95% of your care and attention.
If your keywords are relevant to specific ad groups, and you keep track of which keywords are converting and which aren’t, and when you need to pause/delete them, and you set up your campaigns so your best keywords are treated like the Hollywood Stars they are… then large keyword lists are not a problem, and can be very profitable.