A Sphinn thread reports that in some cases, unpausing a campaigns in an AdWords account can even activate campaigns that have been deleted.

Gab Goldberg summarized the story, saying:

Several AdWords advertisers said they have seen this happen to them in the past. It just sounds like a major bug to me and I don’t see how this can go unnoticed for too long. As AdWords accounts age, some campaigns must be deleted. Often campaigns are paused for one reason or another and when they are unpaused, you can risk being charged for deleted campaigns as well.

This seems like a serious concern to me.

Forum discussion at Sphinn.