Whether it is a required field on the form or not, I have never seen a candidate who had no idea of what salary to expect. If the company/manager/hiring person is not going to mention a salary, the candidate will eventually almost always be forced to mention one, or risk not getting an offer.
So, my advice on this matter is to not fight it, and always be ready with a good number. You can make the range a bit broader if you like, but try making it too broad like 50-100K a year, and you will be spotted right away as trying to be too smart. Just because you mention a range like 60-70K doesn't mean that you will be given the shorter end of it, and plenty of times, employers will even exceed your upper range because that is where their typical salaries are.
Then, there are other kinds of employers who never ask what your expectation is, what range you want, etc, etc, and simply give a hard offer with a number in it, take it or leave it.
[Making this as a community wiki so people can chime in as well.]