The "weight" of a letter is most likely relative. There are over a 100 graduates per year from each of those DO schools. Many of them disappear into the medical world to never be seen again. Others are very active with their old school and donate crazy amounts of money, take students in from that school for little rotations, and are just overall gungho. First off, the most important thing is that they KNOW you. If the school is familiar with the particular person because they are an outstanding and friendly representation of the school, then it will probably help. There are always those people who's stamp of approval may be weighted a little heavier because they have established some level of trust. I have/will have multiple DO letters and I will probably selectively choose which ones I send where. One person was on the adcom for PCOM, another for KCOM, another donates large (LARGE) amounts of money to DMU, and another was for CCOM. They are all very close family friends we have known since I was about 4 years old as well. Most aren't as fortunate as me, but the way I see it...it certainly doesn't HURT. If you can tell they are a complete tool or have no correspondence with their school then I don't think it really matters. A lot of the DOs I've met have been very proud of their school though.