If you're specifically talking about custom forms in request queues, not really. There are certainly workarounds though. For instance, if you specifically want that name of the person submitting the form, consider using or reporting the "Entered By" field instead of creating another custom field for the information.
If you're talking about custom forms in projects, then usually we prefill some static information and save it in a project template.
I don't think we would (or could) do anything with the user.id data string, in either case, other than somehow working around it with a combination of "default settings in selective fields" (radio buttons or checkboxes) and calculated fields.