I agree entirely. Especially in the winter there are always more people than there are spinning bikes, so if someone simply wants to do their own thing and not participate in class then they should choose to spin outside of class time. This is more than rude...in the cases where I've seen this happen (not often) they are quite obviously totally ignoring what the class is doing. Better they spin outside of class and allow someone else to have their bike who wants to be there.