Yeh, What happened to organizing the world's information? I guess that's archive.org's job.

I'm sure the have copies laying around if it's only a TB. But I'm sure google's goal was to shut down a service to cut costs and complexity.

Indeed. The price to keep the information is peanuts.

Take Amazon S3 (at its highest price point, <= 1 TiB):

http://aws.amazon.com/s3/pricing/

($0.125 per GB) * (1 terabyte) = 128 U.S. dollars per month.

I'm surprised Google doesn't want to keep the data available in order to data mine.

They likely do not want to maintain the interface, or the integration of the interface into the overall Google groups interface.