The problem with the ports isn't (in in my experience) with spring-loaded components wearing out: rather, like ceejayoz said, I've seen a number of cases where the port just...moves around inside the device, so that you can't plug the cable in properly. Either it gets offset, so that the port is simply inaccessible through the slot in the case, or pushing in on it just makes the port itself push further into the case. (In that case, one can generally force it in a few times before things start to really break within the case.)

I know of no specific reason why this should be more common with micro-USB than with other connectors, but I've only seen it happen with micro-USB in person.