I have a two-part question.

First, I've been looking for the past year or so for an inexpensive USB charger. A small adapter that'll plug into the wall and has a USB port for my device's cable.

Apple's device is clearly the nicest out there, but the real one costs too much. This one gets close, but I'm still concerned with...

Second, do these devices differ from each other in some way? Like how they're wired? I know some (including the one I link to above) have a higher powered port for charging tablets like the iPad, but is there any other way in which they differ?

I ask because I feel like the Apple charger I have might be dangerous to my Galaxy Nexus. Hear me out here: about 7 weeks ago, I noticed my phone was doing something peculiar. It was showing that it was charging even when it wasn't plugged into anything. Then, it started having trouble charging at all. Eventually I had to replace the phone entirely. Then, about a week after getting the new phone, I had it plugged into the Apple charger again and when I unplugged it I noticed the same thing: the battery icon indicated it was still charging. This freaked me out, and I've since stopped using that charger to charge my phone. I was only using it in the first place because I wanted a charger by our couch so I could plug in my phone while watching TV. I've since swapped it out for another one, and I haven't had the same problem since.

Is there something different Apple's chargers, some chargers in general, or is this just a busted device? If there's something to look for in general, I'd like to know before I stock up on these things. I want to order a bunch of them, so I can keep them all over the place just in case (we use our phones a lot and run out of battery pretty often).

Third (and this is a short one), is there a difference between micro USB cables? Quick example: if I plug my wife's Kindle into my computer with one of my generic Monoprice micro USB cables, the device will charge and that's it. If I plug it in with the original Kindle micro USB cable, the Kindle will charge AND show up as a drive. What's up there?