One of the really strange charges laid against Mises (and sometimes Hayek) is that their honorific "von"s were evidence of their disdain for the common person and that their preferred policies and institutions were really all about enhancing the power of the already powerful. In its most extreme version, it becomes evidence of complicity with fascism. Of course this is nonsense, but it is worth noting that, at least in the early 1960s, Mises did NOT use the "von" when autographing books for friends.
I'm at Liberty Fund today and was perusing the Goodrich collection, and came across Enid Goodrich's copy of Human Action. (Btw, Pierre's copy is there too, along with his copy of The Constitution of Liberty, both of which are heavily annotated and would make a wonderful research project for someone.) Enid's copy is autographed by Mises, as shown below. Clearly Lu didn't think his "von" was so important that he had to use it when signing books. This suggests its relative importance in his self-conception and should be one more reason to dismiss the ridiculous arguments of crazy folks who find unwarranted significance in the "vons."