Interstellar communication is not as impractical as you think. Read Carl Sagan's novel Contact. He talks a lot about how a civilization might structure a message to be useful. Back and forth dialog isn't really possible, but you can broadcast a primer that teaches a language, and the transmit whatever information might be interesting to the recipients (eg. an encyclopedia, or various books). It might take the recipients many years to fully decode and translate the message, but so what? They have time.
Think about this the next time you leave the US on vacation. You have no way of knowing if you have been somehow designated an "enemy combatant".
The major difference between bonds and bond traders is that the bonds will eventually mature.