One of the biggest dangers is that the will may be contested and a court will have to decide if the will is valid or invalid. If the will is invalid, then the estate will have to be administered by using the Intestate laws of Massachusetts, which may not be the way you would to have want your estate handled. You will not know that the will is invalid until after your death and then it is too late, whether it is invalid or not will be up to a judge.
Also, a do it yourself will may not account for contingencies such as pre-deceased children, divorce or the birth of new children. Additionally, if the will is invalid, it may start costly and time consuming litigation that could have a profound effect on the loved ones you left behind, pitting one against another. Finally, without proper consultation from an estate planning lawyer you may not adequately protect your property, because sometimes more complex or different estate planning is necessary other than a simple will.