Datruth, the example is a bit skewed, to say the least. I don't know how many planets have actually been found, but I don't think that more than a couple of star systems have been examined for planets. And while noone has as of yet found an oxygen atom changing into gold, thus noone knows if it is possible (Edit: except if you artificially fuse it to the right amount of protons and neutrons, obviously /Edit), we all know that life is possible. Given then that we can't even make out indvividual star systems in the many distant galaxies, how can you even think of claiming that a sufficient percentage of planets have been examined to disprove possibility of life?
Also, noone as of yet knows if Mars harbours life. Noone knows if it may have done so in the past. Yes, life does need certain properties, and Mars doesn't have them. Not anymore, anyway. It is possible that Mars once had a decent atmosphere containing water, even had oceans. Thus life may have formed, even if it only got to bacteria before Mars lost it's ability to support it. If that is true, then we'd have not only life somewhere in the universe, we'd have had life on two adjacent planets.
Even if not, the presence of both mars and venus shows one thing: that it's certainly not uncommon for planets to be of the right size and at the right distance. So they both are a tad off, but let only one comet hit one of them, and they may change distance and move where earth is ATM. There are plenty of those comets around the universe.
It is assumed that the moon stabilises earth and thus makes life possible. The oon is also assumed to have come from such a collision. It certainly is improbable, but then again, give it not only an innumerable amount of options (AKA, solar systems), but also close to infinite time, and I'm certain that once in a while life will appear. Given that there are galaxies which are just forming, and also galaxies that have existed for ages before this one formed, noone can know what the solar systems will be or have been in the past. Maybe life existed in one of the old galaxies, even, but doesn't anymore? The history of life on earth as we know it is only quite brief compared to the universe.
Also, radio signals as used for everyday communication would get extremely weak when far away from earth. Life would have to be pretty close to this solar system in order to send radio that could be received here AFAICS.
Regarding Tesla, I think he had noticed that resonance is the key to efficiency anywhere. Todays technology rarely makes use of resonance at all. A tuned circuit poses almost no resistance to a signal, thus one would think power transmission could be much more efficient if resonant lines were used. In fact, Tesla suggested the use of high frequency power transmission, and I suspect that it was for exactly this purpose, as well as the fact that with high frequencies, transformers can be significantly smaller. That's BTW why computers use switching power supplies instead of normal ones.
However, the power industry had by that time just finished the adoption of AC transmission (before that, it was DC). IIRC, that also was Tesla's concept. Thus they didn't want to yet again ditch all their equipment. Understandable, but sad, as todays world is stuck with clumsy low frequency power transmission.
This technology you're referring to must be the EM weapon ("death ray") that he allegedly had developed. Teslas Wardenclyffe Tower never was finished, and never even in operation. However, the magnifying transmitter that it was supposed to be is still a bit of a mystery, so it may or may not have caused the Tunguska explosion, be it as weapon test or accident. I think Tunguska was something else, though. Transmitting energy is one thing, but focusing it in one place is something else entirely, especially when you only have one single nondirectional transmitter, so you can't even rely on interference. I might be wrong there, though, since Tesla obviously used different mechanism which may easily have different characteristics and effects.
The free enery things have crept up very often as of yet. One time it's magnets, then it's static electricity, then it's water. I've seen several websites claiming to have a working free energy source, and that it was ready for mass production "by the end of next year". Oddly, I haven't been able to purchase one yet. So if they'd actually have developed one, and managed to keep their website up so long (long enough for me and loads of other people to stumble accross it), wouldn't they also have managed to finish the thing? Of course the governments could have seized the stuff, but if that'd have happened, why would they wait so long? It's surely possible. And if it is the case, then I find it quite humorous that it obviously was the greed of the inventors that enabled the governments to steal it. Had they provided a full disclosure (not the usual stuff that leaves out the crucial parts), and had they posted a link on for example slashdot (even if it stayed online for only a few hours), then there'd have been no way for the knowledge to ever disappear again. Maybe they got scared by the prospect of giving everybody a device to annihilate earth... though in this case, they all choose an interesting point for that realisation. No, I am pretty sure these are fakes.
As for the motor, I have yet to look at it, but I doubt that it manages to retain this performance when a load is connected to it. A motor that doesn't move anything besides itself isn't exactly useful, and usually the power to drive the load us usually much greater than that required to move the motor itself, so whether or not the motor itself puts a strain on the power source doesn't really matter in terms of efficiency. If it converts 99% of it's input power to movement of it's load, then that would be something different entirely.
Edit: I've never heard that antimatter could move faster than normal matter. AFAIK, antimatter didn't have any properties different from matter (except the "polarity" so to speak, obviously).
Edit 2: Oh, BTW: if you were an alien lifeform, capable of movement through the universe to rwach and observe earth, would you not do your best to avoid humanity's attention at all costs? Seriously, humanity is more than PG-18 to intelligent life.
Given that humanity is on the verge of annihilating itself, if life on another planet didn't take radically different directions (meaning more or less a very different concept for nature's and evolution's workings), it very likely wouldn't have developed to the point where it had the option to contact earth before blowing itself up or just damaging it's host planet beyond habitability.