Exomoons versus biosignatures

Some inconvenient truths about biosignatures involving two chemical species on Earth-like exoplanets
http://arxiv.org/abs/1404.6531

A potential false positive for biosignatures involving detection of chemical disequilibrium: it could be the case that the planet has a moon with an atmosphere, in which case both atmospheres could be in equilibrium but give a spectrographic signature of a single object in chemical disequilibrium.

I have to wonder though about the prospects for terrestrial planets to host Titan-like moons...