Most of the comments centered around a possible security threat from Chinese companies buying American companies in various industries, such as the American energy sector that CNOOC tried to enter by bidding for Unocal. Even accepting China as a potential military threat-which is possible but still uncertain- the comments opposing this purchase based on security (or other) reasons were not persuasive.
Some claimed that China could gain important information or even secrets by owning a company like Unocal, but it was never made clear what these were. All pipeline, customer information, etc. is public knowledge, as are most advanced methods for extracting oil and gas. If they need help on gaining access to methods used by other companies, many energy consultants are ready to help them in ways that are fully legal, and are not fully controlled by US policy.
Someone suggested that CNOOC might replace American employees of Unocal with Chinese ones. On the whole, there is nothing to that fear. To be sure, they could bring in some Chinese executives, although that would be at the expense of running the company efficiently. For other employees, They could not get immigration permits to replace the vast majority of Unocal employees in this country.
China does not allow American or other foreign companies to take over Chinese companies in some sectors, or even to enter certain sectors. But why is that a reason for the US opposing CNOOC's bid for Unocal? The case for allowing that bid is that it helps the US for the reasons outlined in my original comment, not that it helps the Chinese, or because of some slavish adherence to principles of "free trade".
Chinese ownership of American companies may not be sufficiently important "hostages" to discourage a military attack on Taiwan or elsewhere. But the point I tried to make on this issue is that China, not America, bears the economic risk from ownership of American assets, since these assets would be taken over by the US in the event of any military conflict, the way German assets in the US were taken over during world War II.
There is evidence, in studies by Solomon Polochek and others, that trade does reduce the probability of conflict between nations, but many other factors are also relevant. So a few examples are not decisive, whether they go in one direction or another. I believe that even the quantitative studies by Polochek and others are far from decisive, but they are the best we have so far.
On an issue raised that is somewhat removed from the main subject, I do believe American airlines should be allowed to fail, as Eastern, Braniff, TWA, and others did fail. To get closer to our present topic, we should remove the obstacles that prevent foreign airlines like BA or Lufthansa from taking over American ones. I believe we should go further, and give many foreign airlines the right to transport passengers between different points within the US.