Sequential object ids tend to create hotspots in a sharded environment. Add the ability to reformat the default object id to make it more pseudo-random. If the time portion of default object id were reversed, then pre-ranging shards would be possible without making hotspots. For example, ten shards, 0 to 9 would be easy to setup to approximate getting rid of hotspots.

In the config file for mongodb, perhaps specifying how the default object should be would be nice. Usually people have to specify the object id in software to get around not being able to shard easily straight out of the box. It would be nice if the default object id would make sharding easy out of the box.