I have built 5 different USB devices and they all worked just fine on my PC, except for the one time I had a short in one. MY PC told me the device would not get power from the USB port and essentially shut it down. Pretty cool!
As far as a USB extender, I have one, and it worked just fine as well. I could not tell any difference than when I was plugging directly into the PC. I also have a 5 and 6 volt power supply that I spliced a USB end on, and those work just fine as well.
So, from my own experience, I have seen no issues with using a USB port or an extender.
I am in the software business now, but have been in the IT field for the past 15 years. I have built PCs and severs for a living, and know them pretty well. As long as you know how to wire them, or buy them from a reputable source, you should be just fine.
It would have been really cool if Tesla's idea of wireless electricity had taken off. We could vape with no cords and recharge at the same time!!!
I also have a car lighter adapter I purchased from some guy in China. It regulates the voltage from 12-36 volts down to 5 volts and 1000mA. It works really well!! If anyone is interested in where I got it, PM me and I will send you the details of the person (I went through ebay). Oh, and the adapter came with a wall plug (I cannot get this to work with any of my USB devices - may be a handshake issue, but not sure), and it also came with an iPod cable. All for just under $6.00 USD!! Beat that, Kensignton!