Seems like everybody is looking at the institutions that can't keep their numbers constant.
Give it a break. Ordinal numbers of chemical elements cannot change, by definition. I may be too optimistic about ISBNs and EANs. Haven't dealt with them and don't know how reliable their issuers are. I guess if they are using their own numbers in a PK in any table that's moderately important, they should catch any duplicates before they make it into the wild. SSNs are issued decentrally, so I'm not surprised they aren't unique; ID cards are issued centrally and managed centrally, so the risk of getting caught in a goof-up is considerably smaller. Oh, and if you're a company caught in the SSN goof-up, using a synthetic key wouldn't have helped in the least. There is no better ID available when it comes to US citizens, so if you're using data from external sources, your data will be goofed up anyway. Things are different if you never use the SSN in external communication to other databases. However, even then you'll never know whether the persons with the same SSN are the same (just changed name and location) or not; there's no better way to identify US citizens, and a synthetic PK won't help you much to resolve that kind of issue!
