Dan Klyn has some practical suggestions for retailers thinking about letting users tag merchandise. Why not pre-populate your catalog with tags drawn from the item descriptions? Why not rank tags higher based on the popularity of the page or item? What do you do about a product that’s tagged “crappy” or “over-priced”? (I think Dan’s answer that last one is that you surface tags based in part on how popular they are.) The result is not a pure folksonomy, but purity isn’t always what we — merchants and shoppers — need.

He also points to Etsy.com as an example of a merchant using tags well.