Currently, when you add a new layer to your TOC it automatically appears in the Selection tab with the checkbox turned 'ON'. This can be problematic when you start editing because you can inadvertantly edit features in layers by unintentionally selecting features in layers that you did not intend to edit. For people who use ArcGIS frequently and do a lot of editing this is obvious and easy to avoid but for users who edit only occasionally they often forget to uncheck the selection of layers they are not interested in. To avoid this issue it would be much safer (for the data) to have new layers automatically unchecked for selection when they are added to the map document. That way the user would have to intentionally turn on the selection of the specific layer(s) they are interested in. Alternatively, a setting that could be set for each user would allow them to control the default behavour to 'ON' or 'OFF' to suit their needs.