It would be useful as a regular user (or superadmin) to be able to set a Dashboard settings (including optionally the period and segment) as read-only.
This would prevent changes to widget position and other settings in context where such dashboards are built for a specific audience (other staff, management, etc.) where any wrong manipulation could accidentally mean unwanted changes difficult or impossible to revert.
Also mentioned here: http://forum.piwik.org/read.php?17,129146
There is a small workaround: