That is soo true.
I have bought one of these off the eBay last year, for approx 90 GBP.
I have copied all my musics, movies, pictures I have collected the last 6-7 years. The hard drive was working very well without any faults. Until my girlfriend wanted to watch some movie, and decided to connect it to her notebook.
Off course it didn`t work, because it needs AC power, it doesn`t get enough just through the USB cable. So she decided to look for a power plug.
(All my chargers, cables are in a box and unfortunately, I didn`t label the power plugs. :bonk

In the first round she ruled out the Western Digital one, because it looked like a phone charger. Finally she found out that her notebook chargers plug fits in the WD-s hole, and she connected the two. :bang::bang:
Since then I have no memories left from the last 6-7 years.
Last month I have found a friend of mine who can possibly recover the data from the damaged hard drive.
Long story short - note to myself:
1. Never buy just only one hard drive especially if you want to back up loads of datas.
2. Never let your girlfriend/wife work alone with your "memories".
3. Label your most important cables/plugs.