1. Limit liability. Each threatened action is made by a separate LLC created just for that purpose. The troll's company is not put at risk every time they want to threaten someone with litigation. The LLC does the dirty work.

2. Make it difficult for the target to assert any sort of leverage. If they do not know who is behind the shell, they do not know what resources the troll may have. If the troll is a practicing entity, they won't know if they have any claims they could assert against the troll. All they see is a recently formed LLC that has certain patent rights, and nothing else.