If the AjaxPagingNavigationIncrementLink should be use with a pagable component without the AjaxPagingNavigator then a WicketRuntimeException is thrown when the link is clicked. The documentation says:
An incremental Ajaxian link to a page of a PageableListView. Assuming your list view navigation looks like
[first / << / <] 1 | 2 | 3 [> / >> /last]
and "<" meaning the previous and "<<" goto the "current page - 5", than it is this kind of incremental page links which can easily be created. This link will update the pageable and itself or the navigator the link is part of using Ajax techniques, or perform a full refresh when ajax is not available.
From that description I understand, that the AjaxPagingNavigationIncrementLink component should work without a AjaxPagingNavigator too, like the non Ajax variant PagingNavigationIncrementLink.
Reason for this is the implementation of the AjaxPagingNavigationBehavior which explicitly searches for the navigator component and throws the exception.