One of my favorite pundits Will Wilkinson, has a piece up on why progressives and libertarians don't mix well, and why conservatives and libertarians tend to group together politically.
In other words, why there are so few RAW-style libertarians who can make common cause with the left on issues such as peace and civil liberties?
Wilkinson argues that it's because libertarians and conservatives has similar attitudes on personal responsibility. As he memorably puts it, "As long as they stick to complaining about handouts for poor people sitting on their asses and praising rich people working hard to make civilization possible, libertarians and conservatives get along fine."
This makes sense to me, but Reason magazine editor Matt Welch dissents.
Addendum: Tyler Cowen explains why one of Matt's points is wrong.