EXIF Data includes data on the shot - date/time/camera/lens/focal length/exposure/ISO/shutter speed compenstation etc... Personally I would be saying leave it in as it helps to get an impression of image and any post shot editing that may have been done. Although people that know how to drive photoshop can replicate the EXIF data anyway. I think it would be good for those that post to post some info on the shot too - lots of people on here want to improve their photography and being able to see examples of photography with good exposure, depth of field etc along with the settings would be educational and beneficial to those people. Not saying that this has to be the case with every competition, maybe though competitions where the images are more serious staged shots than fun ones - if that makes sense.
