Adding/modifying cart line item broadcasts unexpected number of remote events

Description

If anything changes in a cart, a remote event message is sent for the cart, every order form, every shipment, and every line item (times 2 - both cache key for Meta Object as well as cache dependency object used by the catalog content repository).

If running with UDP broadcast, this is unnecessary but not a big problem. But for architechtures such as Amazon, this behavior causes problems with a high "events per second" count on Amazon SQS.

Only events necessary to ensure the data is consistent across instances should be broadcast.