I've been coding in Ruby/Rails for 3 years now, and been active in the community, and I haven't yet done that or encountered anyone who had done that. People are warned that monkey-patching is dangerous, they learn how to monkey-patch responsibly, and they act accordingly and responsibly - if something does go wrong with monkey-patching (which, as I've said, seems not to happen), the person who did the patching is aware of why things are going wrong, and doesn't blame it on the language - I can't remember reading a single query in, say, #rubyonrails, where the problem was due to monkey-patching.