The required view count to avoid auto-deletion of a question when score = 0 is too high.
As an example: http://superuser.com/q/1472443/116475 had 562 views within 1.1 year. This is way more views than average for the site (1 or 2 standard deviations or so), but yet the question was still removed because it didn't have enough views. Currently the rule is "has view count <= the age of the question in days times 1.5."
This threshold makes sense for Stack Overflow, where due to its largeness, people frequent questions a lot more, but doesn't make sense for smaller sites that have lower traffic proportions.
The required view count could instead depend on website-specific view count stats to account for the fact that some SE websites are much less frequented than others (e.g., remove if count is in the lower quartile on the given SE website, or better use human judgments on some question subset to decide).
Example of incorrect deletions caused by Roomba on Android.SE on my account only over the past 60 days (since I joined SE, I've had hundreds of such questions removed):
or on Superuser:
or on WebApps:
Five questions (with zero score) posted by just one user within 60 days were removed, despite most of them receiving an average number of views for the site, just because the overall average views per question on the site is lower than on larger sites.
The following table shows that the median number of views on a question on WebApps is only 42 after 12 months (source, 25%, 50% and 75 are percentiles), which is 13 times less than the Roomba minimum number of views to avoid automated deletion:
Only the top ~10% of the most viewed questions posted on WebApps have more than the Roomba minimum number of views to avoid automated deletion. This means that in practice, if a question has a score of 0 and no answer and less than 2 comments, it'll get deleted.