The Neo-Libertarian looks at complaints over the Cnooc bid for Unocal and notes a real threat… that of the further erosion of the United State’s free-trading credentials:

The argument about the Chinese trying to buy Unocal
provokes hesitance and opposition over the deal from many different
people. The argument from people otherwise disposed to free trade and
open markets is that oil is a strategic asset and China is
untrustworthy or hostile.
Last things first, China isn’t a good country, nor is it a particularly friendly country.  But it’s not a major threat….
Second, if oil is a strategic asset that we shouldn’t be
letting other countries control, then why do we buy over half of ours
from other countries? More to the point, why should those other
countries sell to us? If we try to hoard all the "strategic assets" to
ourselves then so will other countries. If we don’t trust the
international market that we’ve tried to spread around the world, then
why should other countries? We’re not perfect in free trade by any
means, but other countries have needed prodding to get as far as they
have.