One thing I'd like to point out is SETI. A lot of people are talking about SETI's failure to find anything in 30 years. What most are forgetting is that SETI is only checking a very small percentage of the band width we know can function as carrier waves, only the bandwidth we actually use. Technically it's possible there could be a fairly advanced civilization on the "dark" side of the moon that's been there the whole time but doesn't use the same section of the carrier wave bandwidth we do. Much as I love the spirit of SETI it's actually not a very well designed experiment. There are only two ways SETI could ever prove anything conclusively: if they got a hit, or if they radically increased the scope of the experiment. Of course SETI already gets in more data than it can analyze in a reasonable amount of time, so increasing the scope would also increase the analytical delays. It's entirely possible SETI could realize it got a hit years ago but never analyzed that block.
There is even a bigger problem than that. The galactic noise drowns out any possibility of getting a signal below 1Ghz and the Atmosphere above 10Ghz. So we are "stuck" between those two frequencies. A radio telescope on the far side on the moon would be ideal but I haven't the funds to put one there (at least this year LOL!)