Guys, I'm really not trying to be a jerk about this. It just bothers me when I see gross misinformation being peddled as the truth.
That said, I could still be wrong in my opinion on the topic, but so far no one has given a plausible explanation as to why short data cables are problematic. In fact in every other application that I've worked on, there was a concerted effort to limit the length of data cables in order to avoid problems associated with reflections. Here's why:
The size of the reflection is determined by the impedance mismatch and the size of the incident signal. For all practical purposes, the reflection happens instantaneously when an coming voltage transition arrives. If there are mismatches at both ends of the cable, the reflection will bounce back and forth and reduce in amplitude at each reflection. The amount of time that the reflections can affect things is determined by how long it takes for pulses to traverse the cable from one end to the other and back. (Remember that the reflections are instantaneous, but each reflection reduces the amplitude of the reflected signal.) So, the shorter the cable, the less time that the reflections can actually affect the signal that is detected at the destination end of the cable. In that respect, shorter is good. I have never seen an application that required longer cable for better performance unless the additional cable was being used to reduce the signal level of an rf signal that's so large that it will overdrive the front end of the device that will receive it. (For example, GPS receivers don't like too much signal at their input because it can cause intermodulation distortion in their front end amplifiers. So, when hunting for antennas for your GPS receiver, you need to make sure that you don't overdrive the front end by choosing an antenna that has too much gain. On the other hand, if you want to drive a longer cable, you may actually want to use a higher gain antenna to compensate for the additional cable losses that are associated with the increased cable length.)