I too use daily builds of project I'm developing and projects I'm writing.
Just as a suggestion: I use as last digit the following format:
8198 = year + day of year
This gaurantees a unique buildnumber each day, and it shows me (for all me executables exact in which year and on which day the program was generated). I used to use the auto increment of build number, but this produces meaningless numbers.

Seems RAD Studio 2007 and some other similiar product use this rule to name its version number, too?

Sorry for the late reply. I was out for a small holiday.

I don't know about the other products and I haven't used the RAD Studio 2007, yet.

I just needed a way to be able to work on executables each day, giving a select few of users daily builds, with the ability to retain previous versions. It just seemed much more logical than incrementing numbers which does not mean a thing.