Invasion為什麼無第二季？

Main reason is the rating is not good in US. When the show first started, it attracted 17 million viewers, but it dropped to only 9 million viewers when the show showed up to episode 10. So ABC dropped the show.

Rumors said that another channel, the CW channel, would pick invasion up for its 06-07 schedule. However, nothing happened.

For details, you may refer to the site below, you may find the detail infor about the Invasion Incident.
http://www.answers.com/topic/invasion-tv-series

If you really want to show back, you may sign at saveinvasion.net, to save the show wither other Invasion fans.

2006-10-19 16:30:23 補充：
Sorry for answering in English as today my computer's chinese input function is out of order..... Hope you don't mind.