Today I got the hint to take a deeper look into the AD. Surprisingly I found the following entry in the Active Directory Schema [1]:

Sounds like a joke, doesn't it? If you have a look into RFC 1274 [2] search for section 9.3.5. There you will find
9.3.5. Favourite Drink
The Favourite Drink attribute type specifies the favourite drink of
an object (or person).
favouriteDrink ATTRIBUTE
WITH ATTRIBUTE-SYNTAX
caseIgnoreStringSyntax
(SIZE (1 .. ub-favourite-drink))
::= {pilotAttributeType 5}
Seems like it is no joke at all...
[1] http://msdn.microsoft.com/library/default.asp?url=/library/en-us/adschema/adschema/a_drink.asp
[2] http://www.ietf.org/rfc/rfc1274.txt?number=1274