That article on the Pioneer anomaly, http://en.wikipedia.org/wiki/Pioneer_anomaly, made me wonder even more about dark matter. Here is the part about gravitation that caught my attention:
It is possible that deceleration is caused by gravitational forces from unidentified sources such as the Kuiper belt or dark matter. However, this acceleration does not show up in the orbits of the outer planets, so any generic gravitational answer would need to violate the equivalence principle (see modified inertia below). Likewise, the anomaly does not appear in the orbits of Neptune's moons, challenging the possibility that the Pioneer anomaly may be an unconventional gravitational phenomenon based on range from the Sun.
If there is no anomaly in Neptune's moons, then there is no need for dark matter to make those orbits perform as predicted. Does that mean there is no dark matter in our solar system?