1 gbit ether seems quite good with Hadoop
This article seems more like a press release from the infiniband marketing organisation than anything else.
1. Hadoop and MapReduce doesn't need 10 gbit/s to the servers, 1 gigabit is fine for all but the backbone.
2. Facebook have just been describing how they use bittorrent to push out OS images as it scales well on gigabit.
3. 10 gbit/s has a worse power budget and is tricker to keep alive, though optical cabling can save on electricity
When you consider that all the big datacentres appear to be going for JBOD storage on the servers with gigabit interconnect, it's hard to say the trend towards SAN mounted storage and inifiniband is unstoppable.