Why - Delicious of course.

Example: iBegin Source. I can immediately see what people associate the site with. Notice how no one mentions ‘yellow’ for localeze, but mentioned multiple times for Amacai.

So - thats my little secret of the day. Doing keyword research? See how your competitors are being tagged. And the tag cloud sums it up nicely for you.

Yes - this isn’t a direct relationship between user search phrases. But it helps you get into the mind of (a lot of) potential users.