How do I enter Dutch names in Address Book?
My preference is to list their name as something like "Heirseele, van" because when searching by last name you'll still find them using "van" if you decided to. Putting the preposition in another field is a little hackey (and incorrect from a data-integrity point of view) for me.

For the benefit of others: in Dutch, all those prefixes are part of the name. You refer to someone in Dutch as "Meneer van Heirseele" not as "Meneer Heirseele". Those names haven't joined the prepositions like French names have (e.g., Dupré).

Just my two cents…