We have found a lot of clients asking for an alert (Yellow warning to hover over for message) to show on a field in a form when certain conditions have been meet.
One example would be in the SO301000 Sales Order form at the Document Details Tab when a line has the Free Item check box selected a warning would display such as "Please enter Reason Code for Free Item"
This can be accomplished with a customization but wold be much easier to do in the UI.
If a form is added to System Management to add/manage Form Field Messages, this form would have a selector to select the form and field such as in user security. Then a conditions section such as when a filter is added to a primary list and lastly a text entry field to enter the message to display.