I read a paper on ArXiv today about SETI, and talked to Jeremy Darling about water masers. This got me thinking: the best way to signal your presence to the universe as an intelligent civilization is to take advantage of natural amplification. So, say, you go find a big cloud of water molecules in the right state to start masing, and blast them with some of the right frequency radio emission: you get a strongly enhanced isotropic emitter. Maybe SETI should look for those, then search for nearby coherent sources.... EDIT: Isotropic? No.