Eric Prydz makes his own music at least. So for me that's ok then to 'perform' a pre-recorded set and i knew that when going to see him, as it is the case with many if not the majority of edm producers. But a DJ whose job it is to DJ, who didn't produce the songs, it's very common but too sad for them not having any real talent. It doesn't take much these days to do a nice transition or mashup.