From this post: Enable automatic deletion of old, unanswered, zero-score questions after a year?
If the question is more than
30days old, and ...
- has −1 or lower score
- has no answers
- is not locked
...or...
- it was closed and migrated to a different site
... it will be automatically deleted.
TL;DR "Tumbleweed" Questions get automatically deleted as of May 2011
