Bill Burnham writes that the combination means the death of walled gardens:
Much like the delusional King in the Holy Grail, many of the Internets biggest and most profitable Walled Gardens, sites such as Monster.com, Realtor.com, Match.com, and even EBay, appear to be in denial about the ultimate destiny of their sites, which is, that they are bound to be subsumed by the larger Internet.
With Google Base fully in place (and ultimately similar services from Yahoo, Microsoft, and Amazon), why in world would anyone pay to have their listings displayed or pay to have to access to a database of listings? After all, if you publish the listing on your own site Google will automatically index it and then list it within Google Base within the next few days and if you want to make sure they get it immediately, you can just submit if directly to Google Base or register your RSS feed with them (a feature I’ll bet they are likely to add). Instead of charging you (or its end users) for the privilege, Google will make money off of the advertising it sells around the listings. Perhaps you may even be able to pay a fee to have your particular listing advertised in a preferential position.