OK. I looked into this more.
www/admin/ecommerce/cat/category-delete-2.tcl
deletes from quite a few table to make sure no contrainsts are violated. There is no mention of ec_user_session_info in that file.
I cannot find any information about what ec_useer_session_info is actually used for. I don't think it is necessary to save the product and category information in this table. I am not even sure how long it stays in this table anyway.
Should we be removing the references to category and product ids from this table? Basically any time a visitor looks at a product page or category page, it is logged in this table. I cannot remove a product or category if anyone has looked at its page. At least that is what appears to be happening to me.