From their website
“SpyFu lets you see which keywords your competitors are buying and which ones they optimize their site for. Once you understand the competition, you can beat them at their own game or your can exploit their weaknesses. We get our data directly from the source; there are no middlemen. Every month, we extract 125 million ads and search results directly…”
Sounds like an interesting service, peeking into your competitors notebook could certainly give you some ideas.