You can see here the most visited digital camera sites on Alexa: What do you think about this alexa ranking graph? Is it means that this is the beginning of the end for digital camera sites?
I don't know that I would use Alexa as a "trend" tool. I also don't see a number of popular digital camera sites on that graph. Why not use Google Trends? -> Digital Camera Trends Every industry/market has its ups and downs. If those sites are fading off, try to figure out where the audience is going. Other sites? Are they simply funneling their search terms better? Etc.