VLOOKUP better than Relationships? Hell must have frozen over

We always think about a data model with multiple tables and relationships between them as a big improvement over the common practice of combining tables using VLOOKUP expressions. (Watch Video for more: PowerPivot Relationships are EASIER than VLOOKUP, not just faster) I came across a customer request that forced me to admit that in some aspects a VLOOKUP is more flexible than relationships. To solve some specific scenarios we have to use modeling methods which are not elegant and not efficient.