Why does the order of parameters matter for sp_trace_create?
I believe this is because it is an extended stored procedure and the parameter names are actually entirely ignored. It just goes off position.

I have renamed them as below (and given them all the same name) and it still works fine.

DECLARE @new_trace_id INT;

EXECUTE master.dbo.sp_trace_create
  @rubbish = @new_trace_id OUTPUT,
  @rubbish = 0,
  @rubbish = N'C:\temp\TestTrace';

SELECT @new_trace_id AS [@new_trace_id];

EXECUTE master.dbo.sp_trace_setstatus
  @trace_id = @new_trace_id,
  @status = 2;


A similar documentation bug was filed by Aaron about sp_executesql.

Another annoying aspect of that stored procedure is that the @maxfilesize must be passed as 'bigint' and it doesn't accept a literal integer. I assume that this is also because it is an extended stored procedure.