I always leave feedback, and am amazed how few models leave feedback for their photographers and how few photographers for their models.
Surely if this site and its networking function are to be taken seriously and prove useful to as many people as possible, the feedback function is vital.
If a model has images from 6 different togs and shoots and no reference left for her, I have to assume she wasn't very good and don't contact her.
If a tog has taken shots of models on this site and they haven't left feedback I have to assume that the model wasn't happy with the shoot or the photographs so I don't recommend that tog to models who contact me.
I try to work on the 'positive only' comments principle so naturally think it best to leave only positive comments. No comments, to me, indicates negative response, but possibly in some cases could be just laziness.