Thanks to Heidi for posting at SEW forums her question about Content Match ads "disappearing." Apparently this happened when she systematically dropped her bids 5 cents at a time until she was "below the threshold" to compete for contextual positioning.
AdWords Rep came in and replied that it was most likely an issue with the G review/approval process, but it is unsure if that was the case. Other suggestions revolved around the possibility that the bids were too low, as she thought, and that she would have to raise her bid to compete again. The latest post by Heidi explains how she learned that her account was under review but had been "taken off review" on 10/11/05. She has not posted since, so this may have been resolved.
The question that came to mind as I read this was in regards to running a "mirror campaign" within AdWords for Content-only positioning. This means creating Campaign “B” using Campaign “A” keywords and turning “Content network” to off in Campaign “A” (Campaign management page, #5: “Where to show my ads.”) and turning “Search network” off in campaign “B.” I recently tried it with a few Campaigns/Groups for a client, and this seems to have not only increased impressions, but also drastically cut the average cost per click (from approx $1.60 to $0.25 for one group with 371,000 impressions/987 clicks in one recent day). I am curious if others use this tactic effectively. Please comment here or at the SEW Forum thread referenced above.