Sure! I use google anayltics to determine which attributes lead to a sale or other action in my store. Main attribute would be keyword, but there are many others. I can then use this information to determine what to bid on in google adwords.
Good use of analytics can help you figure out areas of your website and marketing campaigns that you might want to focus on. This is especially important for eCommerce sites, but I think it applies to some degree with any website.
Bad data (such as missed sales) in analytics can lead to bad decisions.