Create zero shard sharded setup, attempt to add the first shard without first doing "use admin".
The error message for subsequent shards tell use the user to "use admin" which makes sense. The first shard to be added does the following:

mongos> db.runCommand(

{addShard:"rs1/addShard:charlie-VirtualBox:27012", name:"shard01"}

)
Wed Feb 5 15:15:37.422 error:

{ "$err" : "error creating initial database config information :: caused by :: can't find a shard to put new db on", "code" : 10185 }

at src/mongo/shell/query.js:128

Having the first error message tell the user to use admin is the desired behavior.