Agreed. I'm using the microUSB cables that came with my Kindle and Nook.

However, not ALL will work. I got one of the cheapie ones in a bundle off Ebay from China. It was the AC type. Wouldn't charge at all. Plugged it in and nothing would happen. Some have gotten the bundles and not complained about it. So some work and some don't, its a crap shoot.
I'd say just go to Radio Shack or some other electronics type store and get one. They're not very expensive. Real cheap on Amazon, iirc. (Yup, just did a search for 'micro usb cable' and the first one that came up is $1.79. If you have Amazon Prime, you don't even pay shipping.)
I realize this is an older thread, but I thought I'd relay a recent experience. I was unable to get my PC to recognize the Thunderbolt as a hard drive. After 30 mins on the phone with sprint, the tech asked if I was using the htc cable. I wasn't, but since the cable would charge the phone, I thought it would transfer data. Apparently not. Connecting the htc cable worked right away, as well as a cable from my old Samsung Moment. The "bad" cable has a tag, "charging only" and made in china. Not sure what device it came with.
I wasn't aware that a cable could allow charging but not to connect the devices.