Observers work intermittently in development mode. Specifically with
config.cache_classes = false
in config/environments/development.rb Observers will simply fail to trigger using WEBrick. The whole idea with development mode is having cache_classes = false.
Observers work fine from the console or testing, even in development mode. But do a "reload!" in the console and POOF, Observers are no longer triggered.
This is a very hard bug to track down when it happens. Took me a long time to figure out it was not my code that was broken. This pretty much makes Observers unusable. There's no "agile development" in running with cache_classes = true, just so your code will work during development. Might as well develop in production mode then.
If this bug isn't fixed it at LEAST needs to be mentioned in the docs. It's an invitation to waste people's time not to. Very hard to track down, and you will want to revert all your code once you realize what broke it.
See also:
http://dev.rubyonrails.org/ticket/3558
..issued over a year ago.
