When it comes to Pay-Per-Click (PPC) marketing one size does not fit all. Your industry, your product or service, your budget and your ability to manage the campaign every day will dictate the breadth of your campaign. A campaign with 75 keywords could easily outperform a campaign with 1000 keywords, even though they are built to attract the same type of visitor.
Daily management, testing, and optimization are much more important factors than simply having the most keywords. The fact of the matter is, not all keywords will be successful for you despite how relevant you believe they are to your business. The more you test and optimize your campaign, the easier it will be to identify your best keywords (in addition to recognizing the keywords you need to avoid). I was recently speaking with a potential client who mentioned they had a huge campaign with thousands of keywords and “all their bases” were covered. When I asked about his greatest challenge with the campaign he said that too often he hits his daily budget and his ads stop running. I inquired further and found that he had one large campaign running all his keywords. In Google AdWords, you set your daily budget at the campaign level. If you have all your keywords under one campaign, you run the risk of your best performing keywords being pulled down (and out of the search results) because poor performing keywords cannibalize your overall budget. This is just one of many mistakes I come across when speaking with companies who manage their own PPC campaigns.
For this particular example, think about ways to structure your campaign to maximize the exposure of your best keywords. By doing this, you can limit your liability to keywords that you may find undesirable after sufficient testing. There is no better way to optimize your campaigns than by analyzing real time statistics of your visitors. They will tell you which keywords and ad copy are working and which ones need to be revised or removed. But one size does not fit all and you need to break out your top performers, so their budgets are not compromised by keywords that have high traffic volume and click-through rates (CTR) with little or no conversions.