Which makes re-using the tapes nearly as problematic as throwing them away. (And in most ways more problematic: recycled media remains in use and accessible; at least materials thrown in the trash have a chance of clogging our landfills instead of being mined for unerased data.)
Imation's case rests on the sheer capacity of modern backup media: if even a fraction of a percent of the material on a half-terabyte tape persists after "cleaning," that's multi-megabyte confidential business or personal information headache (or worse) waiting to happen.
The company purchased an assortment of recycled (and supposedly wiped) tapes from the recycled media market, tested them, and found everything from hospital patient records to bank audit information, credit card numbers and more.
Just as Maxell's Halloween backup promotion covered here yesterday recommended using only pristine media, Imation is in the storage media business: both companies are doing business.
But both are also making sound recommendations about storage media re-use, recycling and disposal.
The most dramatic reminder of the persistence of data is also the saddest: a hard disk recovered from the Space Shuttle Columbia disaster yielded readable information.