The definitions of the two were quite distinct in the beginning as others have pointed out. With increasing technological advances, that line has become very blurry. Typically though, to many, communications receivers were considered those that cover the frequency ranges for Long Wave (LW), Medium Wave (MW) and Short Wave (SW), or basically 100 KHz to 30 MHz, or some portion of that range (with a few exceptions). They also tended to have the SSB and CW modes (and maybe even RTTY) on them, as these modes were employed in the shortwave range by various services allocated space. As you have noted, increasingly, manufacturers have been moving the frequency coverage upwards in these receivers, sometimes as high as 3+ GHz, turning them into a new category named "wideband receiver".
Typically, scanners were considered receivers that covered 30 MHz and above, either continuously or in specific ranges. They tended to have memories (channels) allocated in banks (unless they were crytalized) and used mainly to scan these memories. Communications receivers as defined above, were not origianlly designed with memories and were primarily meant to tune continuously through their range rather than scan channels.
So as you can see, manufacturers have now blurred the line separating so called communications receivers from scanners. Nowadays, communications receivers, even if they only cover the LW, MW and SW range usually have memories which you can scan, and some have alpha-tagging. However, they do tend not to have nearly as good of scanning capability as traditional scanners. They tend to scan slower and have fewer memory channels, though I'm sure there are some exceptions to this rule.
The new breed of wideband receivers tend to exhibit weaknesses in performance, usually in the lower frequency ranges of their coverage. It is difficul to design a small radio (particularly handheld) to cover say 100 KHz to 3 GHz and not make compromises. It is going to work well in some areas and not as well in others. I am sure that some of the high-end widebands have been drastically improved since they first appeared on the market. In almost any case that I can think of, a radio designed and dedicated to a specific spectrum range will outperform one that is designed as an all in one. Therefore, I have always been a proponent of having a dedicated LW/MW/SW receiver for anything under 30 MHz and a scanner for anything over it. I feel the performance is so much better when you have dedicated radios, as you get the strengths of each without the compromise of trying to make one work in frequency ranges they just weren't optimally designed for. That being said, some of the high-end desktop widebands may have achieved some measure of good shortwave performance. But at a significant cost to the buyer because of the inclusion of higher quality filtering circuits.
So in reality, they are all communications receivers. They all pick up communications - right? I think it is a matter of semantics, that really is irrelevant in today's market.
