Avraham Bernholz wrote:

Why is the micro USB so fragile compared to mini USB cable ends?

I bought a bunch of micro-USB cables recently from Frys, and
almost half of them have had the two little nubs on the top
of the male micro-USB connector disappear.

It's deliberate ... with USB and miniUSB the contacts and retaining
springs are in the socket and wear out after 1,000 to 2,000 insertions;
with microUSB the wear is intended to happen within the plug, because
the cable can be more easily replaced, they're also rated for more like
10,000 insertions.

I have sometimes managed to persuade the "nibs" back into life with the
end of pin, but cables are cheap.