In the article you referred to

by sea.bass - 3/4/12 5:18 AM

In Reply to: "...who's going to bother?" by btljooz

I found

"On the other hand, according to the 2006 NIST Special Publication 800-88 (p. 7): "Studies have shown that most of today's media can be effectively cleared by one overwrite" and "for ATA disk drives manufactured after 2001 (over 15 GB) the terms clearing and purging have converged."[1] An analysis by Wright et al. of recovery techniques, including magnetic force microscopy, also concludes that a single wipe is all that is required for modern drives. They point out that the long time required for multiple wipes "has created a situation where many organisations ignore the issue all together - resulting in data leaks and loss. "[5]

Pretty reassuring.