SETI won't work
The search for extra-terrestrial intelligence (SETI) is running a long term programme that searches through radio telescope data for signals that could have been produced by extra-terrestrial intelligent sources (little green men, if you want). You can participate in this search by going to the SETI at home site, and downloading the software there. A few years ago I began to run this SETI software as a screen saver on my PC, but I never found any extra-terrestrial intelligence, and nor has anyone else.
After staring at this screen saver for longer than most sane people would consider healthy, it became obvious that the search strategy that SETI uses is totally naive, and it is bound to fail in its goal. In a nutshell, what SETI looks for are transmissions that resemble carrier signals, which are the signals that are sent out by transmitters which you "tune into" when you twiddle the dial on your radio (or press the auto-search button). Actually, SETI is rather cleverer than that, because a transmitter is likely to be moving on a curved path (e.g. it is on a planet orbiting about a star) which will make the frequency of its carrier signal vary with time, so the search takes account of the variations in the carrier frequency that this causes.
Why is searching for carrier signals a naive strategy for SETI to use?
The answer is that an intelligent transmitter would not use such an inefficient way of transmitting signals. Also, they might not want anyone to eavesdrop on their signals, so they would use a more stealthy means of communication. The most obvious alternative possibility is something that we humans already do; it is called spread spectrum transmission, which was (surprisingly!) invented by the actress Hedi Lamarr. The trick is to not use one carrier frequency, but to use a random sequence of many carrier frequencies, thus spreading the transmitted signal over the frequency spectrum in a way that makes it very difficult to receive if you don't know the random sequence used. If you combine this with appropriate "whitening" of the transmitted signal, then the spread spectrum signal is indistinguishable from background noise, and it is actually impossible to receive if you don't know the random sequence and the whitening method used. Generally, a transmitter is at its most efficient in terms of both bandwidth and stealth when its transmissions look like white noise, and the means used to achieve this could be much more sophisticated than merely being simple variations of the frequency hopping approach described above.
If we are already using spread spectrum techniques ourselves, then it is likely that an extra-terrestrial civilisation would be doing something that is at least as clever, and probably far cleverer. This is why SETI won't work.
In this week's New Scientist there is an article Looking for alien intelligence in the computational universe in which Stephen Wolfram makes the same criticism of the SETI search strategy. He then proposes that we do a search of the universe of all possible algorithms (i.e. the computational universe) for ones that have behaviours that are a cyber-version of an extra-terrestrial civilisation. This is an application of A new kind of science. Wolfram's proposal is that a cyber-version of an extra-terrestrial civilisation is as good as the real thing. This is complete rubbish, and I am surprised that he offers this as a serious proposal. It is like saying that virtual reality is the same as real reality. They might seem to be the same but they are not actually the same.
I think that the computational universe is a very worthwhile place to harvest, because there will be algorithms out there that do very interesting and useful things, and which could be used as the basis for whole new technologies. This is why A new kind of science is a very good thing that more people should pay attention to. However, this has nothing whatsoever to do with SETI.
I will caveat that last remark. There is the possibility that there are algorithms out there in the computational universe that might be used as a sophisticated way of encoding/decoding transmissions, and which extra-terrestrial civilisations might already be using. All we need to do is to find these algorithms, and we can then eavesdrop on the extra-terrestrial conversation, assuming there are no other gotchas standing in the way, such as the very interesting scenario that is described in Piers Anthony's book Macroscope; read the book, especially if your IQ is 150+.
SETI should focus on reality and not create a virtual simulacrum of reality. Remember that science is about connecting with experimental results; computational simulations are very interesting in the same way that pure maths is interesting, but without an anchor in reality they are not actually science. This distinction is the same as the difference between natural philosophy (now discredited) and natural science.
SETI should also extend their search strategy to look beyond communication using mere carrier waves, otherwise they are going to waste an awful lot of computer time hunting through the radio telescope data.