People need to remember, you constantly got to get value from the data you are storing as it does cost you money to store. Storage is cheap they say, but your paying for it constantly. If you only get a nugget of information once and a while, then how long do you need to keep the data for. If you have data going back 20 years, is it skewing the results.
My personal opinion is that we need to keep smaller subsets of data, a realistic purging point where data makes no sense to keep indefinitely. I think we also need to have some idea on what question we want to ask of our data to ensure the appropriate data is kept.
Regards,
Hawk65
PS: Look at the organisations that tell you to keep all data, standing behind them are large storage or software organisations.