I got my Nook in April, 2012. Loved it, immediately! Worked out great for me.
Recently, in July, 2012, the charger for my Nook, wouldn't work. I plugged it in, the light came on, but the Nook, it's self, wouldn't charge, I have a warranty, so, B&N sent me a replacement wire and plug, free.
It worked perfect untill, last week. Sept.1,2012. It happened again. I got another replacement sent to me.
I plugged it into my laptop, tried different wall outlets, nothing. This time, the screen, while plugged in was going from "will charge in 15 min," to plug into an outlet." I called, and they decide to send me a replacement NOOK. Suppose to get it, tomorrow. Was on the phone with the yesterday. Their customer service is amazing!!!
Not happy I had to have replacements, before a year of having the product. I treate it so nice. Never dropped it. I got stick on me a lot. I didn't use a card or have many things on it. Pretty disappointed.
Solid state electronic devices are subject to unexpected failures. It is called the "infant mortality" problem because the failures usually occur within the first several months after a device in put into use. Manufacturers try their best to prevent such failures via various manufacturing and QA procedures, but it is not possible to eliminate them completely. Even NASA is not immune from hardware failures.
I reckon its likely that a lot more important than whether you've dropped it is how gingerly you've inserted the micro-USB plug.
That is, the extended micro-USB plug is a common failure point. The extra length seems to give it extra leverage in either bending the plug, or widening the port, increasing the play, or both. A mini-USB would have been a lot more stable but since they are likely to be even thinner with the Nook Tablet version 2 to be released Q4, likely announced sometime next month, that ship has probably sailed. Even the style of plug where the charger is detected by shorting out the data and clock lines on a high capacity micro-USB cable with a regular length micro-USB plug would likely be more robust.