A good example of this is the Ideas Application, which define the assignement field like this:
this field is of type List Of Users, and a a wiki with thousand of users, it cause the request to run for so long that it timeout. This made the Ideas Application unusable on a wiki with lot of users.
The same is obviously true for any list field type that could return a very large list of potential values.
We have a couple of options:
1) timeout the preparation of the list somehow, returning an erreur, but ensuring it does not runs for hours.
2) switching to a text filter when there is too many items for a list filter
3) disallowing list filter on list field type that is not static