I agree with Phil, read only should not be fields. It is considered better practice now to say up front 'All fields are required unless stated otherwise' or similar and clearly mark optional fields. If you don't need to ask something then you really shouldn't ask it.
Once again, I refer to you exhaustive research carried out by Luke Wroblewski http://www.lukew.com/resources/articles/WebForms_LukeW.pdf (this is a link to a PDF).
The link above has become outdated, but this link serves the same information:
Marking Required vs. Optional form fields - Luke Wroblewski