In this official Apple support document, Apple lists the limits on calendars and reminders, contacts, and bookmarks.
For example, here are just a few of the limits on contacts:
– Total number of contact cards: 50,000
– Maximum size of a contact card: 256 KB
– Maximum size of a contact photo: 224 KB
– Maximum size of a contact group: 256 KB
[Via 512 Pixels]
What the heck? Those limits are tiny.
I should google this, but I wonder how this compares with the vanilla CardDAV spec.
I just pulled a couple of contacts onto my desktop; one (with minimal information) is only 4 KB, and the other (my own, which has a sizable amount of stuff in it) is a whopping 94 KB.
256 KB is pretty small for most things, but contact cards are pretty tiny themselves.