[Mulder]

These systems generate a huge amount of data. In order to store this information for a longer time would require the cellular carriers to make huge expenditures in data storage infrastructure hardware and software...with no return on these expenditures.

So the federal gov't will store it.

Also, I think the data storage requirements are a lot less than most people think.

[Bloody Sam Roberts]

"Also, I think the data storage requirements are a lot less than most people think."

I am currently in the data storage infrastructure biz. The expenditures for data storage for this type of information on a large scale are not insignificant. For them (the carriers), to commit to storing this data long term, without significant expansion of current operations, would heavily tax whatever current data storage personnel and equipment they have.
I have also worked for a major cellular carrier and I know the setup and how the stuff works.