This paper describes the results of a series of subjective experiments that investigated the annoyance caused by the most common artifacts present in segmented video sequences. Various types of artifacts were inserted into a reference segmented video considered as ideal and shown to our test subjects. The artifacts varied in their location, size, appearance and duration. Annoyance of segmentation artifacts are found to be tied up with their intrinsic characteristics (e.g., size, position) but only weakly related to the video content. The results identify the characteristics that should be taken into account in the design of a perceptually driven objective metric.