Nothing may excuse it, but to take two infamous examples where entities sued based on fraudulent assertions of copyright ownership, as determined in court, the

Nothing may excuse it, but to take two infamous examples where entities sued based on fraudulent assertions of copyright ownership, as determined in court, the SCO Group and Righthaven (https://en.wikipedia.org/wiki/Las_Vegas_Review-Journal#Copyright_infringement https://en.wikipedia.org/wiki/Las_Vegas_Review-Journal#Copyr...), nothing serious happened to the plaintiffs, other than of course losing their lawsuits and going bankrupt. (Others have mentioned Prenda Law, but that cit's behavior was so aberrant it's not a very useful example.)