Reasons not to use an auto-incrementing number for a primary key

Question

I\'m currently working on someone else\'s database where the primary keys are generated via a lookup table which contains a list of table names and the last primary key used

Answer 1

It's useful for clients to be able to pre-allocate a whole bunch of IDs to do a bulk insert without having to then update their local objects with the inserted IDs. Then there's the whole replication issue, as mentioned by Galwegian.