The 'we' in this thread title refers to our solar system.
An article in New Scientist : 14 May 2011 page 47 (paper copy)
It reviews the results of extra-solar planet finding, with over 200 planets so far discovered in a little under 200 star systems. The surprise finding is that nothing like our solar system has yet been discovered.
Our solar system is atypical. We have a system with small rocky planets close to the sun, and large gas giants further out. All are in almost circular orbits, moving in a well behaved, stately way, around the sun. And of course, we have Earth in the liquid water belt, also in a beautiful, stable, almost circular orbit.
Other stellar systems have all kinds of different systems. Giant planets orbiting very close to their parent star are common. Wildly eccentic and elliptical orbits. Planets massively bigger than Jupiter. Every indication of violent interactions between bodies within those systems.
Our solar system is not normal. It is wildly different. It is stable in a way few others are. Our beautiful circular orbits are not normal. The size of our planets and the palaces they orbit are not normal. Is our solar system just weird?
And what are the implications for finding life in any other stellar system?