I had put some thought into this yesterday. It was my iGoogle quote. My wife and I actually had a discussion about it last night. I was reminiscing a story I had read several years back. I don't remember it clearly, but don't worry... I'll fill the missing details with my own vision.
Short form: There once was an intent to design a spacecraft that could be lifelike in this way. You would send out, say 10. If one were to make a successful landing somewhere where it was able to gather supplies for power and production, then it would begin production of itself until it ran out of one or the other, power or building materials. Each of the spacecraft that it built would be sent out blindly with the same instruction set as the last. These would maintain hop style communication with one another. People tend to like immediate answers to life's questions though. So, that fact that this would take a long time to produce many if any, coupled with the fact the just the communication would be slow and exponentially slower per generation keeps this from being feasible.
Off topic. Anyway, I think it is pretty fallacious, but I still love this guy, and I think that the quote has some merit. I think viruses are a bit embarrassing to mankind, but it is really just an addition the the laundry list of horrible things we've accomplished; not life.