I've seen quite a few complaints on the xda-developers board about people with various Android phones and tablets (Nexus 7 included) becoming more or less unusable because the microUSB port wears out after so many thousand plug-ins and eventually breaks, dislodges, or stops recognizing the cable, and the end-user is unable to charge their device anymore.
Since I wirelessly charge my Nexus 7 90% of the time (only using micro-USB if travelling or topping it off at work), the micro-USB port is still in great condition. Personally I've had four phones and two tablets and never had any of the ports break on me, but, I suppose fumbling in the dark trying to jam the cable into the phone late at night could definitely put some wear and tear on the device.
I've heard possible stories that wireless charging might be worse for the battery, though, so, trade-offs for everything I suppose.