For all the sites I maintain, I have at least a local and production environment. Some projects warrant a dev, qa, etc. as well, but for the purposes of this post, let's just assume you often run drush commands on local or development environments during development, and eventually run a similar command on production during a deployment.
What happens if, at some point, you are churning through some Drush commands, using aliases (e.g.
drush @site.local break-all-the-things to break things for testing), and you accidentally enter
@site.prod instead of
@site.local? Or what if you were doing something potentially disastrous, like deleting a database table locally so you can test a module install file, using
drush sqlq to run a query?
$ drush @site.prod break-all-the-things -y<br />
Everything is broken! [sadpanda]<br />