When a MySQL client or the mysqld server receives a packet bigger than max_allowed_packet bytes, it issues a Packet too large error and closes the connection. With some clients, you may also get a Lost connection to MySQL server during query error if the communication packet is too large.
Default server configuration is 1MB. For larger sites, it needs to be increased to MEDIUMBLOB (16MB).
Know this is not high priority, but wanted to chime in and mention that I'm seeing this pretty often.