reading John Gruber's account, I had a couple of ideas on what to do about it.
- in Finder, when a file has a custom “Open With” assocation on it, badge the file's icon with the application icon. in this case, it would have the Terminal icon badged onto it.
- in Safari, add a new warning when a file contains an “Open With” that points to an application that wouldn't normally handle that type of file. in this case, Terminal does not normally open JFIF files, and this should cause a warning.