I don't think a blacklist could possibly be comprehensive enough. I think you'd have to use some OS permission-limiting system to prevent it and any subprocesses it spawns from have any write access to the filesystem.
Of course, much more thought is needed to try something like this. Somebody could as well use awk with its system command to do whatever..
This would save you, for example, if you had a custom command called "gr" which was short for "get rid of current directory" (obviously chosen as a pathological example since it's a prefix of grep). As you type the word "grep", auto-running is paused because "g", "gr", and "gre" are not whitelisted, and then once "grep" is fully typed, it recognizes that "grep" is on the whitelist and resumes auto-running. And it never ran the dangerous "gr" command.
...? :D