Security ("Oh, I'm sorry, sir, go ahead. I didn't realise you were root") still reads pretty well today. Vi might no longer read its conf file from the CWD, but the standard toolkit has plenty of SUID=0 programs: this vanilla Debian has 17 of them in /bin:/usr/bin. Of these, only sudo really benefits from being architected in this way. Cf. http://lwn.net/Articles/199004/ for another approach.