I too have been burned by the BBOC, although not as badly as this:

I picked out a random short ethernet cable that looked nice (it was flat) to connect my wifi AP to my router.

It took me about a month to realize my 100mbit internet connection had dropped down to about ~85-90mbit, but more importantly, transferring files between a wifi client and the wired network was also only ~90mbit.

Turned out the cable was so bad that it only connected at 100mbit...

I have now gone the other way and I actually curate the BBOC: All cables I get for 'free' with random appliances now go straight to the bin (unless they are specialised) and I only keep cables I specifically bought and know they adhere to a standard.