That's where it would be nice to be able to counter sue for legal expenses, under the theory that the C&D lawyer is abusing his position as an officer of the court in writing a baseless C&D letter (thereby causing the target to have to hire a lawyer to review the issue). So even if this wouldn't happen that often, it would be something they would have to consider prior to writing a letter with baseless claims.

Of course, being lawyers, they would probably put in some fine print that states that no legal threat is implied, or something like that.