I spent years in Java prior to Ruby and through the various frameworks in Java, I never remember making the mistake or working with anyone who made the mistake of blowing away the production data when running tests.
Since working in Rails, have had at least 2-3 experiences on the team with truncated/dropped tables or mangled data in production, and it isn't just the current team.
Many other languages and frameworks don't have it as part of the normal process used by most developers to accidentally do this as much as it has seemed to happen in Rails 2, due to the conventions used.
With Rails, the same project for the most part is in dev, test, and prod. Developers want database.yml revisioned with the rest of the app. Many Rails developers at some point run production against production DB locally, in order to run migrations on production prior to Capistrano deploys, etc., or maybe just to run a production console to run reports or tweak data. So, there is a very real chance for wild things to happen in such a risky environment. I'm not anti-Rails by any means, but I've not heard of this happening as much as it has historically with Rails in other frameworks.