Yahoo!'s decision to purchase del.icio.us, the popular social bookmarking startup, has sparked plenty of media coverage with this story in News.com and this one from The Associated Press.

The acquisition -- which John Battelle speculates cost Yahoo! about $35 million -- does have a Seattle angle. That's because Seattle-based Amazon.com -- along with Union Square Capital, BV Capital and others -- was an early investor in del.icio.us. So my question is this: Why did Amazon.com take a stake in del.icio.us if it wasn't interested in gobbling up the service?

Did the bidding get too rich? Does the service not fit with Amazon.com's strategy? Does the online retailer have its own technology? Or is Amazon not interested in expanding through acquisitions?

UPDATE: Here's a message from Amazon.com (dated November 11) which explains how it is using tagging technology. And here is a little more commentary on the topic from Daniel Terdiman at News.com. Basically, Amazon.com now allows some of its customers to tag -- or classify -- certain products so that they are easily accessible. The online retailer also holds an equity stake in Robot Co-op, the Seattle startup that allows users to tag their favorite places or products through 43places.com and 43things.com