Lil' Wayne appeared on more than 70 tracks and mixtapes last year. And Jay-Z will guest on an upcoming Coldplay song, repaying singer Chris Martin for appearing on the rap mogul's "Kingdom Come." With guest appearances quickly becoming the norm and not the exception, we ask New York times pop critic Jon Caramanica why cameos are so prevalent in hip hop.

Soundcheck blog: When hip hop cameos reach the point of diminishing returns