Why USB-mini? Here's why
I'll tell you why for ME, at least, a USB mini plug is mandatory. I use my MP3 player as a mass storage flash drive. It goes in my pocket along with my cell phone. In order to plug it into a machine when I'm moving around at the office or at home, I do NOT want to have to remember to bring my proprietary cable with me, and I'm not about to pay extra to have more than one at different locations. With a mini USB port, if there isn't a cable readily available, all I have to have with me is one of those little USB-to-USBmini adaptors, a less than an inch long. If I'm afraid the MP3 player will put too much weight on the adaptor or port because it won't rest on the desktop when plugged in, I use a flexible male-to-female adaptor and it hangs down so it can reach the desktop. DONE.
I agree with JK98 that they should be able to incorporate a USB-mini plug into a proprietary design if they want to make docking possible. By the way I dock mine without a proprietary port. I bought a Hummingbird all-in-one USB hub and card reader. The hub is a little disc-shaped base. The card reader sits vertically in a notch in the top of the hub. They connect via a little USB-mini plug (not port) sticking up in the bottom of the notch. My MP3 player sits in the notch right on that plug just fine.