Yes, marketers can use tiny AdWords campaigns as a form of cheap focus group, but it is like log files, you will have only the metrics on keywords you're promoting using your Search Engine Optimization work or the ones you choose in your Adwords campaign but no data on keywords you'll dont used in your marketing efforts. But I got to admit the Adwords is the better way to have a fast feedback on your keywords than SEO.
But two of the "old" good ways to get a good feedback by peoples, and without any cost except your times, is to choose the right newsgroups or the goods rooms in a chat. With thoses, you'll have even a faster response and with a lot of more details and interaction. And like Adwords, you can choose the geolocation of your audience!