Speaking of which, do the current SETI programs check for signal modulation using polarization.
Speaking of SETI, their current intent is to do a distributed computation spread across thousands of computers, similar to some of the keycracking efforts. Details at http://www.bigscience.com ; the Recent News section says they're currently trying to figure out about funding. Meanwhile, there's www.mersenne.org for factoring big prime numbers.
One of the problems I have with SETI is that it assumes that a distant civilization is sending out a beacon for others to home in on, and that this beacon is a narrowband signal. What if most such civilizations aren't looking for anyone and merely going about their own affairs, including communications for their own needs? Because of path losses it takes an incredibly strong narrowband signal to traverse even relatively small cosmological distances and have any hope of detection with our technology. For example, Earth's strongest TV signals could be detected by our present technology out to about 50 light years, but no image reconstruction would be possible (insufficient S/N). The highest power transmitter-directional antenna, at Aricebo, can be heard to about 300 light years, but its only transmitted a SETI beacon once and only for a few minutes. An excellent way to mitigate path loss is trading bandwidth for data rate. GPS garners an incredible 63 dB of process gain (or about a 2,000,0000 fold improvement) in this manner. If I was trying to send a electromagnetic signal vast distances I'd use some form of spread spectrum. Individually, narrowband receivers are most insensitive to broadband 'noise' sources. However, I wonder if it might be possible to configure the SETI@home software to coordinate the narrowband channels signal analysis so as to have a better chance of detecting broadband, pseudo-noise, signaling. --Steve