LData:
Luis E. and I did extensive testing of Ldata back in the day. Some of the more heinous side effects were corruption of collections, and vertical application collections (specifically ADT). What was apparently happening, if say a block had ldata attached to it, there was a strong possibility for the Blocks collection to become corrupted. It was severe in the Vertical application collections (ADT WallStyles, etc.) because these "collections" are defined in AEC_ dictionaries.
I don't know the how, I don't know if it's been fixed, but I had to reconstitute a major part of an architectural project I was working on due to LData. I'll never use it again.