At what stage should acknowledgements be inserted into the paper if review is not double-blind? When the review process is double-blind, I guess (although I have not read this anywhere) that acknowledgements should not be written in the submitted paper, as this might break anonimity. They should only be inserted into the camera-ready version, after the paper is accepted.

What is the custom when the review process is not double-blind? Should I write the acknowledgements in the submitted version, or wait to the camera-ready version?
If it's not double-blind, then it generally doesn't matter whether the acknowledgements are in the initial version or not: the reviewers will simply ignore them.

When there are page limits involved, however, I like to put the acknowledgements in as early as possible.  That way, their size is built in from the beginning and we don't have to figure out how to fit the extra space during the revision.