Mine burnt through last year (after three years) and i didn't review it. A friend of mine has got her third in two years and didn't review either. This is exactly what happens:

"I've had two adapters break on me, the wire somehow shorts out and melts near the "square". Really poor design, love the computers but the adapters are terrible." (one of the reviews)

The wire is super thin, i'm not saying it's planned obsolescence, but it's close.

edit: english