Just a quick point of view from the other side of the fence: once, whilst I was an ATC assistant at Shawbury the local flying club flew a number of us around the local area as a liasion exercise. I remember it vividly because it is the only time I have been worried whilst flying. Having got airborne I suddenly realised that I couldn't see any other aircraft. Why did this worry me? Because not 15 minutes earlier I had been standing looking over the Shawbury Zone Controller's shoulder and could see how busy the airspace was. However, the "big sky theory" soon took over and the feeling went away - it just proves that a little knowledge can be dangerous.
Conversely, don't get to fixated on listening for conflictions on the R/T. I have had (professional) pilots query me giving them descent (in Class G under RAS) because they had also heard me give descent to another aircraft to the same level when the aircraft were over 60 miles apart going to destinations (oil rigs) 40 miles apart. However, having said that, if you have the slightest doubt about what ATC is asking you to do then please ask the question. It saves a lot of paperwork!