Also consider that each ventrue's feeding restriction isn't going to be random, it's going to be something personally significant to them. It's either going to be a type of person they're highly attracted to, a member of a group that they're proud to be a part of, or someone who's home culture they were heavily effected by.

The ventrue shouldn't have a lot of trouble identifying people they're feeding-restricted to because they should already be significant to them for other reasons.