If any of the collections, containers, or elements in the Windows Live Contacts schema exceeds its quota, then Window Live Contacts returns the "409 Conflict" status code.
The quota of each object in the schema is listed in Windows Live Contacts API: REST Schema Details, with these additional constraints:
Contact collections
6500
MSGR tags (Groups) per address book
100
ContactID per Group
1000
Active contact subscribers for each profile
Tags (categories) for each address book
200
The maximum number of objects (collections, containers, or elements) that can be inserted in a single POST request is one object.