colony:
1. a group of people who leave their native country to form in a new land a settlement subject to, or connected with, the parent nation.
...
6. any group of individuals having similar interests, occupations, etc., usually living in a particular locality; community: a colony of artists.
http://dictionary.reference.com/browse/colony

Should humans have colonies in Space?

Life would be more dangerous if there were colonies in space.

In today's world an individual or nation would have difficult time killing everyone.
Technology of biological and nuclear weapons has made it easier to kill a lot of people.
But even a total war involving nukes and biological weapon would only kill billions of people,
perhaps most people but not much more than 99.9%.
A few centuries ago, warfare could not kill a high percentage of the world population- plagues
that could accompany war generally killed more soldiers and civilians
"French soldiers were attacked by yellow fever during the 1802 Haitian Revolution; more than half of the army perished from the disease." -Wiki. Napoleon's army was defeated mostly by disease.
And historically, armies often were destroyed or defeated by disease.

But people in space could have the power to fairly easily kill large numbers of people living on Earth and could even kill everyone on Earth. They even could also *accidentally* kill everyone on earth. Though of course without any human involvement everyone on Earth could be killed in a similar accidental manner.

The percentage of people who would want to kill large numbers of people is small, but there a larger percentage of people willing to threaten to kill large numbers of people. And as with human nature the people who would *merely* choose to threaten to kill large number of people can "develop" in various ways into those one would actually do this. So it's not just the ax murdering psychopath that gets meaning from life by torturing and/or killing someone, it's those who are willing to threaten to kill someone to gain power/wealth- or for instance, the type of person who would do anything to get a million dollars.

In our morally debased modern civilization, one could argue that there too many people who do anything for a million [or billion] dollars, therefore, space colonies are not desirable.