IMHO extraterrestrial life exists but we'll never discover it because the distances are to big. So other life can not become dangerous. (As far as they have the same physics as we think we have: Einstein's thoughts)
A beacon sould only contain one single piece of information: 'contact us friendly'. Our planet is sending so many signals of every kind that our earth itself is a beacon. So sending a beacon is not necessary.
I run SETI@home so I can be told if I'm wrong with my opinion ;)
SETI@home and Astropulse are funded by grants from the National Science Foundation, NASA, and donations from SETI@home volunteers. AstroPulse is funded in part by the NSF through grant AST-0307956.
