Voyager 2 - More like a blog post than I realized
The Voyager mission was designed to take advantage of a rare geometric arrangement of the outer planets in the late 1970s and the 1980s which allowed for a four-planet tour for a minimum of propellant and trip time. The flyby of each planet bends the spacecraft's flight path and increases its velocity enough to deliver it to the next destination.
JPL Fact Sheet - California Institute of Technology
This technique of using the local planet's gravity to accelerate the craft to the next planetary rendezvous is a little like viral theory. The "gravity assist" technique, which was first demonstrated with NASA's Mariner 10 Venus/Mercury mission in 1973-74, and shortened the flight time to Neptune from 30 years to 12 years, multiplies the forward momentum of the craft. It also modifies the trajectory to expose the craft to new destinations. A blog post that spreads from reader to reader and is re-blogged to new blogs builds its momentum forward to new destinations.
Whereas the astronomers and astrophysicists and other scientists at the Jet Propulsion Laboratory at Cal Tech can calculate the effect of trajectory and successive 'gravity assists,' we bloggers still craft a message to unknown recipients, publish it to the Internet, hope someone reads it and either responds or relays it forward so that another can read it... and respond. Better than a message in a bottle cast to the outgoing tide, but not yet as scientific or successful as exploration of interstellar space.