I'm co-editor for a niche news site (http://pokerfuse.com) and we strictly do not write any headlines in the "is...?" format. It's a good check before publishing anything - if your headline naturally falls in to this format, it should be a signal that either (a) we shouldn't be writing this story, (b) we should stand by our convictions and write the headline in the affirmative, (c) the story needs more research before publishing. We pass up on some easy pageviews, but we see the upside in more loyal/repeat visitors.
why would you insist on starting with an "Is"? A proper yes or no question can start with "Is", "Are", "Does", "Do", "Have", "Has", "Were", "Did", etc etc. How many of your titles end with a question-mark? It's hard to think of how any of those can be false positives.
edit:
NewsItem.objects.published().count()
>>> 648
NewsItem.objects.published().filter(title__istartswith='is', title__endswith='?').count()
>>> 2
(a couple of stories do have this format, but they seem like the rare appropriate cases)