While Hadoop may cut the margin Google gained from its innovation of using parallel processing to cut computing costs, the catch-up claims are being overdone.
The reason is that Google will keep innovating. Its genius does not lie in any particular technology, but in its focus and its fostering an environment where innovators can market-test their ideas quickly.
Geocities. Yoyodyne. Broadcast.com. All were much better deals for the sellers than Yahoo, which bought them in the 1990s. No wonder Yahoo itself seems to be in the acquisition crosshairs, this time of Microsoft.
It's the speed of getting ideas to market that separates Google from the pack. You can't buy that. You can only build it by empowering innovators. Sometimes it takes time for such innovation to be monetized. See YouTube.
Open source empowers innovators organically. Everyone is free to work on what interests them, and the Internet gets these ideas to the world as fast as they're created.
After watching Yahoo for 10 years I'm convinced they'll never learn.